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	$152.92	5.494%	$161.3214	$161.32	$161.30	$161.30
Purchase #2	$222.33	3.860%	$230.9119	$230.91	$230.90	$230.90
Purchase #3	$33.56	8.580%	$36.4394	$36.44	$36.45	$36.40
Purchase #4	$22.54	13.792%	$25.6487	$25.65	$25.65	$25.60
Purchase #5	$69.78	4.427%	$72.8692	$72.87	$72.85	$72.90
Purchase #6	$221.39	4.731%	$231.864	$231.86	$231.85	$231.90
Purchase #7	$149.37	11.743%	$166.9105	$166.91	$166.90	$166.90
7 purchase totals =	$871.89		$925.9651	$925.96	$925.90	$925.90