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	$48.38	11.732%	$54.0559	$54.06	$54.05	$54.10
Purchase #2	$213.39	4.569%	$223.1398	$223.14	$223.15	$223.10
Purchase #3	$248.34	11.348%	$276.5216	$276.52	$276.50	$276.50
Purchase #4	$179.80	9.821%	$197.4582	$197.46	$197.45	$197.50
Purchase #5	$111.91	6.224%	$118.8753	$118.88	$118.90	$118.90
Purchase #6	$139.80	12.529%	$157.3155	$157.32	$157.30	$157.30
Purchase #7	$206.70	7.815%	$222.8536	$222.85	$222.85	$222.90
7 purchase totals =	$1,148.32		$1,250.2199	$1,250.23	$1,250.20	$1,250.30