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	$152.86	9.279%	$167.0439	$167.04	$167.05	$167.00
Purchase #2	$135.57	9.380%	$148.2865	$148.29	$148.30	$148.30
Purchase #3	$37.38	7.357%	$40.13	$40.13	$40.15	$40.10
Purchase #4	$52.36	5.625%	$55.3053	$55.31	$55.30	$55.30
Purchase #5	$37.29	8.748%	$40.5521	$40.55	$40.55	$40.60
Purchase #6	$12.87	4.683%	$13.4727	$13.47	$13.45	$13.50
Purchase #7	$177.63	4.425%	$185.4901	$185.49	$185.50	$185.50
7 purchase totals =	$605.96		$650.2806	$650.28	$650.30	$650.30