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	$218.73	3.466%	$226.3112	$226.31	$226.30	$226.30
Purchase #2	$82.62	10.435%	$91.2414	$91.24	$91.25	$91.20
Purchase #3	$236.30	11.515%	$263.5099	$263.51	$263.50	$263.50
Purchase #4	$162.78	5.344%	$171.479	$171.48	$171.50	$171.50
Purchase #5	$30.54	10.392%	$33.7137	$33.71	$33.70	$33.70
Purchase #6	$201.50	10.222%	$222.0973	$222.10	$222.10	$222.10
Purchase #7	$123.43	8.775%	$134.261	$134.26	$134.25	$134.30
7 purchase totals =	$1,055.90		$1,142.6135	$1,142.61	$1,142.60	$1,142.60