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	$97.64	3.353%	$100.9139	$100.91	$100.90	$100.90
Purchase #2	$212.81	13.633%	$241.8224	$241.82	$241.80	$241.80
Purchase #3	$52.92	10.537%	$58.4962	$58.50	$58.50	$58.50
Purchase #4	$222.94	7.833%	$240.4029	$240.40	$240.40	$240.40
Purchase #5	$234.50	10.614%	$259.3898	$259.39	$259.40	$259.40
Purchase #6	$145.64	13.510%	$165.316	$165.32	$165.30	$165.30
Purchase #7	$104.89	4.559%	$109.6719	$109.67	$109.65	$109.70
7 purchase totals =	$1,071.34		$1,176.0131	$1,176.01	$1,175.95	$1,176.00