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	$100.30	11.121%	$111.4544	$111.45	$111.45	$111.50
Purchase #2	$57.50	6.490%	$61.2318	$61.23	$61.25	$61.20
Purchase #3	$141.44	4.212%	$147.3975	$147.40	$147.40	$147.40
Purchase #4	$179.59	9.446%	$196.5541	$196.55	$196.55	$196.60
Purchase #5	$89.45	12.637%	$100.7538	$100.75	$100.75	$100.80
Purchase #6	$155.78	10.218%	$171.6976	$171.70	$171.70	$171.70
Purchase #7	$243.43	13.223%	$275.6187	$275.62	$275.60	$275.60
7 purchase totals =	$967.49		$1,064.7079	$1,064.70	$1,064.70	$1,064.80