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	$216.80	3.849%	$225.1446	$225.14	$225.15	$225.10
Purchase #2	$228.83	9.819%	$251.2988	$251.30	$251.30	$251.30
Purchase #3	$116.45	12.608%	$131.132	$131.13	$131.15	$131.10
Purchase #4	$240.76	6.392%	$256.1494	$256.15	$256.15	$256.10
Purchase #5	$93.79	12.698%	$105.6995	$105.70	$105.70	$105.70
Purchase #6	$176.56	7.631%	$190.0333	$190.03	$190.05	$190.00
Purchase #7	$241.77	11.793%	$270.2819	$270.28	$270.30	$270.30
7 purchase totals =	$1,314.96		$1,429.7395	$1,429.73	$1,429.80	$1,429.60