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	$95.94	5.213%	$100.9414	$100.94	$100.95	$100.90
Purchase #2	$195.50	7.339%	$209.8477	$209.85	$209.85	$209.80
Purchase #3	$28.57	10.749%	$31.641	$31.64	$31.65	$31.60
Purchase #4	$203.58	3.394%	$210.4895	$210.49	$210.50	$210.50
Purchase #5	$148.88	9.253%	$162.6559	$162.66	$162.65	$162.70
Purchase #6	$215.28	11.691%	$240.4484	$240.45	$240.45	$240.40
Purchase #7	$55.82	11.260%	$62.1053	$62.11	$62.10	$62.10
7 purchase totals =	$943.57		$1,018.1292	$1,018.14	$1,018.15	$1,018.00