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	$87.62	9.419%	$95.8729	$95.87	$95.85	$95.90
Purchase #2	$218.32	4.327%	$227.7667	$227.77	$227.75	$227.80
Purchase #3	$53.61	10.113%	$59.0316	$59.03	$59.05	$59.00
Purchase #4	$80.47	10.669%	$89.0553	$89.06	$89.05	$89.10
Purchase #5	$92.26	9.146%	$100.6981	$100.70	$100.70	$100.70
Purchase #6	$143.48	3.629%	$148.6869	$148.69	$148.70	$148.70
Purchase #7	$76.82	3.241%	$79.3097	$79.31	$79.30	$79.30
7 purchase totals =	$752.58		$800.4212	$800.43	$800.40	$800.50