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	$44.95	3.740%	$46.6311	$46.63	$46.65	$46.60
Purchase #2	$29.94	8.732%	$32.5544	$32.55	$32.55	$32.60
Purchase #3	$56.52	5.171%	$59.4426	$59.44	$59.45	$59.40
Purchase #4	$191.38	10.837%	$212.1199	$212.12	$212.10	$212.10
Purchase #5	$128.36	13.394%	$145.5525	$145.55	$145.55	$145.60
Purchase #6	$210.45	10.176%	$231.8654	$231.87	$231.85	$231.90
Purchase #7	$199.60	11.567%	$222.6877	$222.69	$222.70	$222.70
7 purchase totals =	$861.20		$950.8536	$950.85	$950.85	$950.90