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	$164.52	5.557%	$173.6624	$173.66	$173.65	$173.70
Purchase #2	$69.61	3.669%	$72.164	$72.16	$72.15	$72.20
Purchase #3	$66.69	6.718%	$71.1702	$71.17	$71.15	$71.20
Purchase #4	$246.65	9.874%	$271.0042	$271.00	$271.00	$271.00
Purchase #5	$11.51	11.183%	$12.7972	$12.80	$12.80	$12.80
Purchase #6	$202.64	10.120%	$223.1472	$223.15	$223.15	$223.10
Purchase #7	$174.69	9.544%	$191.3624	$191.36	$191.35	$191.40
7 purchase totals =	$936.31		$1,015.3076	$1,015.30	$1,015.25	$1,015.40