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	$40.82	5.374%	$43.0137	$43.01	$43.00	$43.00
Purchase #2	$87.59	5.115%	$92.0702	$92.07	$92.05	$92.10
Purchase #3	$212.35	8.319%	$230.0154	$230.02	$230.00	$230.00
Purchase #4	$30.72	6.758%	$32.7961	$32.80	$32.80	$32.80
Purchase #5	$175.36	7.388%	$188.3156	$188.32	$188.30	$188.30
Purchase #6	$99.55	12.434%	$111.928	$111.93	$111.95	$111.90
Purchase #7	$233.25	7.443%	$250.6108	$250.61	$250.60	$250.60
7 purchase totals =	$879.64		$948.7498	$948.76	$948.70	$948.70