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	$66.29	7.650%	$71.3612	$71.36	$71.35	$71.40
Purchase #2	$244.30	8.454%	$264.9531	$264.95	$264.95	$265.00
Purchase #3	$234.51	12.443%	$263.6901	$263.69	$263.70	$263.70
Purchase #4	$33.58	9.519%	$36.7765	$36.78	$36.80	$36.80
Purchase #5	$173.65	10.187%	$191.3397	$191.34	$191.35	$191.30
Purchase #6	$58.69	6.687%	$62.6146	$62.61	$62.60	$62.60
Purchase #7	$116.45	12.565%	$131.0819	$131.08	$131.10	$131.10
7 purchase totals =	$927.47		$1,021.8171	$1,021.81	$1,021.85	$1,021.90