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	$100.51	10.404%	$110.9671	$110.97	$110.95	$111.00
Purchase #2	$168.48	10.514%	$186.194	$186.19	$186.20	$186.20
Purchase #3	$47.48	6.614%	$50.6203	$50.62	$50.60	$50.60
Purchase #4	$160.97	7.278%	$172.6854	$172.69	$172.70	$172.70
Purchase #5	$10.37	12.558%	$11.6723	$11.67	$11.65	$11.70
Purchase #6	$39.47	12.751%	$44.5028	$44.50	$44.50	$44.50
Purchase #7	$159.31	8.290%	$172.5168	$172.52	$172.50	$172.50
7 purchase totals =	$686.59		$749.1587	$749.16	$749.10	$749.20