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	$85.50	12.220%	$95.9481	$95.95	$95.95	$95.90
Purchase #2	$56.62	3.859%	$58.805	$58.81	$58.80	$58.80
Purchase #3	$20.30	11.167%	$22.5669	$22.57	$22.55	$22.60
Purchase #4	$173.49	6.701%	$185.1156	$185.12	$185.10	$185.10
Purchase #5	$90.41	11.570%	$100.8704	$100.87	$100.85	$100.90
Purchase #6	$202.85	3.470%	$209.8889	$209.89	$209.90	$209.90
Purchase #7	$68.98	6.491%	$73.4575	$73.46	$73.45	$73.50
7 purchase totals =	$698.15		$746.6524	$746.67	$746.60	$746.70