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	$152.72	6.110%	$162.0512	$162.05	$162.05	$162.10
Purchase #2	$67.47	12.803%	$76.1082	$76.11	$76.10	$76.10
Purchase #3	$37.53	8.697%	$40.794	$40.79	$40.80	$40.80
Purchase #4	$168.83	11.524%	$188.286	$188.29	$188.30	$188.30
Purchase #5	$249.89	6.623%	$266.4402	$266.44	$266.45	$266.40
Purchase #6	$229.36	7.474%	$246.5024	$246.50	$246.50	$246.50
Purchase #7	$111.55	7.623%	$120.0535	$120.05	$120.05	$120.10
7 purchase totals =	$1,017.35		$1,100.2355	$1,100.23	$1,100.25	$1,100.30