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	$81.81	11.849%	$91.5037	$91.50	$91.50	$91.50
Purchase #2	$85.74	7.146%	$91.867	$91.87	$91.85	$91.90
Purchase #3	$95.77	3.319%	$98.9486	$98.95	$98.95	$98.90
Purchase #4	$225.94	9.841%	$248.1748	$248.17	$248.15	$248.20
Purchase #5	$65.95	12.732%	$74.3468	$74.35	$74.35	$74.30
Purchase #6	$173.65	4.857%	$182.0842	$182.08	$182.10	$182.10
Purchase #7	$190.61	13.593%	$216.5196	$216.52	$216.50	$216.50
7 purchase totals =	$919.47		$1,003.4447	$1,003.44	$1,003.40	$1,003.40