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	$48.44	9.362%	$52.975	$52.98	$53.00	$53.00
Purchase #2	$89.36	10.177%	$98.4542	$98.45	$98.45	$98.50
Purchase #3	$185.97	7.502%	$199.9215	$199.92	$199.90	$199.90
Purchase #4	$141.85	7.489%	$152.4731	$152.47	$152.45	$152.50
Purchase #5	$14.57	13.329%	$16.512	$16.51	$16.50	$16.50
Purchase #6	$221.27	10.143%	$243.7134	$243.71	$243.70	$243.70
Purchase #7	$219.71	8.263%	$237.8646	$237.86	$237.85	$237.90
7 purchase totals =	$921.17		$1,001.9138	$1,001.90	$1,001.85	$1,002.00