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	$86.39	3.314%	$89.253	$89.25	$89.25	$89.30
Purchase #2	$168.61	13.388%	$191.1835	$191.18	$191.20	$191.20
Purchase #3	$226.81	11.761%	$253.4851	$253.49	$253.50	$253.50
Purchase #4	$190.96	9.751%	$209.5805	$209.58	$209.60	$209.60
Purchase #5	$200.70	10.375%	$221.5226	$221.52	$221.50	$221.50
Purchase #6	$239.70	6.684%	$255.7215	$255.72	$255.70	$255.70
Purchase #7	$159.29	12.424%	$179.0802	$179.08	$179.10	$179.10
7 purchase totals =	$1,272.46		$1,399.8264	$1,399.82	$1,399.85	$1,399.90