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	$73.25	8.839%	$79.7246	$79.72	$79.70	$79.70
Purchase #2	$145.34	9.651%	$159.3668	$159.37	$159.35	$159.40
Purchase #3	$235.92	3.274%	$243.644	$243.64	$243.65	$243.60
Purchase #4	$46.66	13.606%	$53.0086	$53.01	$53.00	$53.00
Purchase #5	$203.26	9.814%	$223.2079	$223.21	$223.20	$223.20
Purchase #6	$25.54	6.379%	$27.1692	$27.17	$27.15	$27.20
Purchase #7	$207.64	10.714%	$229.8865	$229.89	$229.90	$229.90
7 purchase totals =	$937.61		$1,016.0076	$1,016.01	$1,015.95	$1,016.00