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	$230.87	5.507%	$243.584	$243.58	$243.60	$243.60
Purchase #2	$47.63	8.222%	$51.5461	$51.55	$51.55	$51.50
Purchase #3	$79.75	12.531%	$89.7435	$89.74	$89.75	$89.70
Purchase #4	$51.73	3.680%	$53.6337	$53.63	$53.65	$53.60
Purchase #5	$206.30	7.250%	$221.2568	$221.26	$221.25	$221.30
Purchase #6	$211.40	6.837%	$225.8534	$225.85	$225.85	$225.90
Purchase #7	$57.39	13.719%	$65.2633	$65.26	$65.25	$65.30
7 purchase totals =	$885.07		$950.8808	$950.87	$950.90	$950.90