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	$151.89	5.105%	$159.644	$159.64	$159.65	$159.60
Purchase #2	$164.91	5.239%	$173.5496	$173.55	$173.55	$173.50
Purchase #3	$40.54	11.503%	$45.2033	$45.20	$45.20	$45.20
Purchase #4	$83.30	6.859%	$89.0135	$89.01	$89.00	$89.00
Purchase #5	$185.82	6.379%	$197.6735	$197.67	$197.65	$197.70
Purchase #6	$170.83	13.809%	$194.4199	$194.42	$194.40	$194.40
Purchase #7	$179.31	5.331%	$188.869	$188.87	$188.85	$188.90
7 purchase totals =	$976.60		$1,048.3728	$1,048.36	$1,048.30	$1,048.30