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	$93.39	6.682%	$99.6303	$99.63	$99.65	$99.60
Purchase #2	$33.41	10.522%	$36.9254	$36.93	$36.95	$36.90
Purchase #3	$36.57	10.596%	$40.445	$40.45	$40.45	$40.40
Purchase #4	$159.89	6.153%	$169.728	$169.73	$169.75	$169.70
Purchase #5	$226.93	4.286%	$236.6562	$236.66	$236.65	$236.70
Purchase #6	$231.82	13.360%	$262.7912	$262.79	$262.80	$262.80
Purchase #7	$212.59	13.284%	$240.8305	$240.83	$240.85	$240.80
7 purchase totals =	$994.60		$1,087.0066	$1,087.02	$1,087.10	$1,086.90