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	$196.63	5.434%	$207.3149	$207.31	$207.30	$207.30
Purchase #2	$242.27	7.676%	$260.8666	$260.87	$260.85	$260.90
Purchase #3	$47.42	11.362%	$52.8079	$52.81	$52.80	$52.80
Purchase #4	$158.36	5.123%	$166.4728	$166.47	$166.45	$166.50
Purchase #5	$137.26	11.568%	$153.1382	$153.14	$153.15	$153.10
Purchase #6	$173.30	13.626%	$196.9139	$196.91	$196.90	$196.90
Purchase #7	$101.49	8.455%	$110.071	$110.07	$110.05	$110.10
7 purchase totals =	$1,056.73		$1,147.5853	$1,147.58	$1,147.50	$1,147.60