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	$191.52	6.588%	$204.1373	$204.14	$204.15	$204.10
Purchase #2	$223.82	5.841%	$236.8933	$236.89	$236.90	$236.90
Purchase #3	$44.96	11.612%	$50.1808	$50.18	$50.20	$50.20
Purchase #4	$84.90	11.162%	$94.3765	$94.38	$94.40	$94.40
Purchase #5	$238.89	6.704%	$254.9052	$254.91	$254.90	$254.90
Purchase #6	$27.92	13.451%	$31.6755	$31.68	$31.70	$31.70
Purchase #7	$40.60	3.505%	$42.023	$42.02	$42.00	$42.00
7 purchase totals =	$852.61		$914.1916	$914.20	$914.25	$914.20