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	$170.43	12.333%	$191.4491	$191.45	$191.45	$191.40
Purchase #2	$63.95	12.749%	$72.103	$72.10	$72.10	$72.10
Purchase #3	$50.94	7.732%	$54.8787	$54.88	$54.90	$54.90
Purchase #4	$225.95	5.371%	$238.0858	$238.09	$238.10	$238.10
Purchase #5	$234.26	3.509%	$242.4802	$242.48	$242.50	$242.50
Purchase #6	$242.91	4.613%	$254.1154	$254.12	$254.10	$254.10
Purchase #7	$204.88	11.735%	$228.9227	$228.92	$228.90	$228.90
7 purchase totals =	$1,193.32		$1,282.0349	$1,282.04	$1,282.05	$1,282.00