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	$132.80	6.385%	$141.2793	$141.28	$141.30	$141.30
Purchase #2	$136.94	10.766%	$151.683	$151.68	$151.70	$151.70
Purchase #3	$69.25	10.489%	$76.5136	$76.51	$76.50	$76.50
Purchase #4	$105.98	8.164%	$114.6322	$114.63	$114.65	$114.60
Purchase #5	$105.50	13.300%	$119.5315	$119.53	$119.55	$119.50
Purchase #6	$91.82	8.766%	$99.8689	$99.87	$99.85	$99.90
Purchase #7	$190.67	10.610%	$210.9001	$210.90	$210.90	$210.90
7 purchase totals =	$832.96		$914.4086	$914.40	$914.45	$914.40