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	$71.96	4.148%	$74.9449	$74.94	$74.95	$74.90
Purchase #2	$127.47	13.317%	$144.4452	$144.45	$144.45	$144.40
Purchase #3	$28.54	13.682%	$32.4448	$32.44	$32.45	$32.40
Purchase #4	$184.80	3.406%	$191.0943	$191.09	$191.10	$191.10
Purchase #5	$29.95	11.585%	$33.4197	$33.42	$33.40	$33.40
Purchase #6	$122.64	4.825%	$128.5574	$128.56	$128.55	$128.60
Purchase #7	$11.36	10.480%	$12.5505	$12.55	$12.55	$12.60
7 purchase totals =	$576.72		$617.4568	$617.45	$617.45	$617.40