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	$243.90	7.654%	$262.5681	$262.57	$262.55	$262.60
Purchase #2	$123.70	3.727%	$128.3103	$128.31	$128.30	$128.30
Purchase #3	$67.28	9.570%	$73.7187	$73.72	$73.70	$73.70
Purchase #4	$230.43	6.137%	$244.5715	$244.57	$244.55	$244.60
Purchase #5	$128.64	13.695%	$146.2572	$146.26	$146.25	$146.30
Purchase #6	$111.61	3.824%	$115.878	$115.88	$115.90	$115.90
Purchase #7	$58.64	4.459%	$61.2548	$61.25	$61.25	$61.30
7 purchase totals =	$964.20		$1,032.5586	$1,032.56	$1,032.50	$1,032.70