Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$228.98	8.521%	$248.4914	$248.49	$248.50	$248.50
Purchase #2	$151.92	10.280%	$167.5374	$167.54	$167.55	$167.50
Purchase #3	$120.96	8.447%	$131.1775	$131.18	$131.20	$131.20
Purchase #4	$91.85	9.626%	$100.6915	$100.69	$100.70	$100.70
Purchase #5	$167.26	11.574%	$186.6187	$186.62	$186.60	$186.60
Purchase #6	$244.63	11.665%	$273.1661	$273.17	$273.15	$273.20
Purchase #7	$189.82	10.192%	$209.1665	$209.17	$209.15	$209.20
7 purchase totals =	$1,195.42		$1,316.8491	$1,316.86	$1,316.85	$1,316.90