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	$50.97	3.802%	$52.9079	$52.91	$52.90	$52.90
Purchase #2	$212.47	3.401%	$219.6961	$219.70	$219.70	$219.70
Purchase #3	$62.90	7.416%	$67.5647	$67.56	$67.55	$67.60
Purchase #4	$32.47	3.371%	$33.5646	$33.56	$33.55	$33.60
Purchase #5	$75.39	9.303%	$82.4035	$82.40	$82.40	$82.40
Purchase #6	$39.61	11.468%	$44.1525	$44.15	$44.15	$44.20
Purchase #7	$230.25	11.345%	$256.3719	$256.37	$256.35	$256.40
7 purchase totals =	$704.06		$756.6612	$756.65	$756.60	$756.80