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	$187.89	11.735%	$209.9389	$209.94	$209.95	$209.90
Purchase #2	$89.35	5.857%	$94.5832	$94.58	$94.60	$94.60
Purchase #3	$115.59	13.600%	$131.3102	$131.31	$131.30	$131.30
Purchase #4	$166.93	6.244%	$177.3531	$177.35	$177.35	$177.40
Purchase #5	$36.62	5.340%	$38.5755	$38.58	$38.60	$38.60
Purchase #6	$131.86	13.123%	$149.164	$149.16	$149.15	$149.20
Purchase #7	$245.51	6.196%	$260.7218	$260.72	$260.70	$260.70
7 purchase totals =	$973.75		$1,061.6467	$1,061.64	$1,061.65	$1,061.70