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	$205.45	9.675%	$225.3273	$225.33	$225.35	$225.30
Purchase #2	$43.36	6.218%	$46.0561	$46.06	$46.05	$46.10
Purchase #3	$37.86	11.258%	$42.1223	$42.12	$42.10	$42.10
Purchase #4	$195.72	6.484%	$208.4105	$208.41	$208.40	$208.40
Purchase #5	$11.50	7.250%	$12.3338	$12.33	$12.35	$12.30
Purchase #6	$83.91	5.627%	$88.6316	$88.63	$88.65	$88.60
Purchase #7	$122.50	12.160%	$137.396	$137.40	$137.40	$137.40
7 purchase totals =	$700.30		$760.2776	$760.28	$760.30	$760.20