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	$249.69	3.555%	$258.5665	$258.57	$258.55	$258.60
Purchase #2	$115.74	12.423%	$130.1184	$130.12	$130.10	$130.10
Purchase #3	$6.72	6.457%	$7.1539	$7.15	$7.15	$7.20
Purchase #4	$162.59	6.313%	$172.8543	$172.85	$172.85	$172.90
Purchase #5	$103.84	7.718%	$111.8544	$111.85	$111.85	$111.90
Purchase #6	$197.99	13.115%	$223.9564	$223.96	$223.95	$224.00
Purchase #7	$39.71	10.523%	$43.8887	$43.89	$43.90	$43.90
7 purchase totals =	$876.28		$948.3926	$948.39	$948.35	$948.60