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	$85.26	3.343%	$88.1102	$88.11	$88.10	$88.10
Purchase #2	$101.48	12.471%	$114.1356	$114.14	$114.15	$114.10
Purchase #3	$34.46	9.720%	$37.8095	$37.81	$37.80	$37.80
Purchase #4	$11.50	8.227%	$12.4461	$12.45	$12.45	$12.40
Purchase #5	$171.59	7.538%	$184.5245	$184.52	$184.50	$184.50
Purchase #6	$162.46	5.809%	$171.8973	$171.90	$171.90	$171.90
Purchase #7	$119.87	5.421%	$126.3682	$126.37	$126.35	$126.40
7 purchase totals =	$686.62		$735.2914	$735.30	$735.25	$735.20