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	$200.34	11.366%	$223.1106	$223.11	$223.10	$223.10
Purchase #2	$164.89	11.776%	$184.3074	$184.31	$184.30	$184.30
Purchase #3	$20.71	4.627%	$21.6683	$21.67	$21.65	$21.70
Purchase #4	$132.36	11.221%	$147.2121	$147.21	$147.20	$147.20
Purchase #5	$98.61	12.645%	$111.0792	$111.08	$111.10	$111.10
Purchase #6	$219.74	13.406%	$249.1983	$249.20	$249.20	$249.20
Purchase #7	$195.29	4.709%	$204.4862	$204.49	$204.50	$204.50
7 purchase totals =	$1,031.94		$1,141.0621	$1,141.07	$1,141.05	$1,141.10