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	$154.55	12.727%	$174.2196	$174.22	$174.20	$174.20
Purchase #2	$192.61	6.195%	$204.5422	$204.54	$204.55	$204.50
Purchase #3	$110.60	11.496%	$123.3146	$123.31	$123.30	$123.30
Purchase #4	$150.86	13.733%	$171.5776	$171.58	$171.60	$171.60
Purchase #5	$211.93	3.778%	$219.9367	$219.94	$219.95	$219.90
Purchase #6	$174.25	12.220%	$195.5434	$195.54	$195.55	$195.50
Purchase #7	$98.50	8.746%	$107.1148	$107.11	$107.10	$107.10
7 purchase totals =	$1,093.30		$1,196.2489	$1,196.24	$1,196.25	$1,196.10