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	$43.66	10.407%	$48.2037	$48.20	$48.20	$48.20
Purchase #2	$238.27	6.756%	$254.3675	$254.37	$254.35	$254.40
Purchase #3	$188.86	4.167%	$196.7298	$196.73	$196.75	$196.70
Purchase #4	$214.79	4.238%	$223.8928	$223.89	$223.90	$223.90
Purchase #5	$16.62	4.256%	$17.3273	$17.33	$17.35	$17.30
Purchase #6	$233.62	6.773%	$249.4431	$249.44	$249.45	$249.40
Purchase #7	$42.30	7.822%	$45.6087	$45.61	$45.60	$45.60
7 purchase totals =	$978.12		$1,035.5729	$1,035.57	$1,035.60	$1,035.50