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	$48.55	7.532%	$52.2068	$52.21	$52.20	$52.20
Purchase #2	$166.40	11.268%	$185.15	$185.15	$185.15	$185.20
Purchase #3	$91.74	9.749%	$100.6837	$100.68	$100.70	$100.70
Purchase #4	$57.82	4.573%	$60.4641	$60.46	$60.45	$60.50
Purchase #5	$159.82	7.484%	$171.7809	$171.78	$171.80	$171.80
Purchase #6	$226.27	12.218%	$253.9157	$253.92	$253.90	$253.90
Purchase #7	$181.41	12.489%	$204.0663	$204.07	$204.05	$204.10
7 purchase totals =	$932.01		$1,028.2675	$1,028.27	$1,028.25	$1,028.40