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	$99.54	13.243%	$112.7221	$112.72	$112.70	$112.70
Purchase #2	$79.65	11.328%	$88.6728	$88.67	$88.65	$88.70
Purchase #3	$7.53	5.377%	$7.9349	$7.93	$7.95	$7.90
Purchase #4	$134.47	5.558%	$141.9438	$141.94	$141.95	$141.90
Purchase #5	$111.89	5.751%	$118.3248	$118.32	$118.30	$118.30
Purchase #6	$101.30	10.837%	$112.2779	$112.28	$112.30	$112.30
Purchase #7	$143.71	13.284%	$162.8004	$162.80	$162.80	$162.80
7 purchase totals =	$678.09		$744.6767	$744.66	$744.65	$744.60