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	$131.75	4.619%	$137.8355	$137.84	$137.85	$137.80
Purchase #2	$173.85	8.636%	$188.8637	$188.86	$188.85	$188.90
Purchase #3	$48.94	4.626%	$51.204	$51.20	$51.20	$51.20
Purchase #4	$229.84	10.646%	$254.3088	$254.31	$254.30	$254.30
Purchase #5	$111.33	11.673%	$124.3256	$124.33	$124.35	$124.30
Purchase #6	$12.33	12.812%	$13.9097	$13.91	$13.90	$13.90
Purchase #7	$104.89	3.109%	$108.151	$108.15	$108.15	$108.20
7 purchase totals =	$812.93		$878.5983	$878.60	$878.60	$878.60