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	$160.48	11.126%	$178.335	$178.34	$178.35	$178.30
Purchase #2	$171.25	13.240%	$193.9235	$193.92	$193.90	$193.90
Purchase #3	$195.75	13.648%	$222.466	$222.47	$222.45	$222.50
Purchase #4	$170.53	8.142%	$184.4146	$184.41	$184.40	$184.40
Purchase #5	$186.61	13.648%	$212.0785	$212.08	$212.10	$212.10
Purchase #6	$22.94	12.347%	$25.7724	$25.77	$25.75	$25.80
Purchase #7	$77.73	6.812%	$83.025	$83.03	$83.05	$83.00
7 purchase totals =	$985.29		$1,100.0150	$1,100.02	$1,100.00	$1,100.00