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	$32.98	10.512%	$36.4469	$36.45	$36.45	$36.40
Purchase #2	$165.86	4.243%	$172.8974	$172.90	$172.90	$172.90
Purchase #3	$118.40	4.244%	$123.4249	$123.42	$123.40	$123.40
Purchase #4	$131.50	6.346%	$139.845	$139.85	$139.85	$139.80
Purchase #5	$233.73	12.146%	$262.1188	$262.12	$262.10	$262.10
Purchase #6	$126.63	8.399%	$137.2657	$137.27	$137.25	$137.30
Purchase #7	$50.32	6.185%	$53.4323	$53.43	$53.45	$53.40
7 purchase totals =	$859.42		$925.4310	$925.44	$925.40	$925.30