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	$89.67	7.489%	$96.3854	$96.39	$96.40	$96.40
Purchase #2	$203.31	13.221%	$230.1896	$230.19	$230.20	$230.20
Purchase #3	$142.80	7.493%	$153.5	$153.50	$153.50	$153.50
Purchase #4	$134.39	12.850%	$151.6591	$151.66	$151.65	$151.70
Purchase #5	$151.52	11.394%	$168.7842	$168.78	$168.80	$168.80
Purchase #6	$110.88	5.662%	$117.158	$117.16	$117.15	$117.20
Purchase #7	$170.40	8.851%	$185.4821	$185.48	$185.50	$185.50
7 purchase totals =	$1,002.97		$1,103.1584	$1,103.16	$1,103.20	$1,103.30