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	$41.56	9.319%	$45.433	$45.43	$45.45	$45.40
Purchase #2	$18.92	3.553%	$19.5922	$19.59	$19.60	$19.60
Purchase #3	$98.87	12.603%	$111.3306	$111.33	$111.35	$111.30
Purchase #4	$63.57	8.644%	$69.065	$69.07	$69.05	$69.10
Purchase #5	$212.71	4.557%	$222.4032	$222.40	$222.40	$222.40
Purchase #6	$227.82	9.623%	$249.7431	$249.74	$249.75	$249.70
Purchase #7	$42.72	10.689%	$47.2863	$47.29	$47.30	$47.30
7 purchase totals =	$706.17		$764.8534	$764.85	$764.90	$764.80