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	$194.79	9.359%	$213.0204	$213.02	$213.00	$213.00
Purchase #2	$50.66	8.736%	$55.0857	$55.09	$55.10	$55.10
Purchase #3	$33.43	10.872%	$37.0645	$37.06	$37.05	$37.10
Purchase #4	$82.51	8.738%	$89.7197	$89.72	$89.70	$89.70
Purchase #5	$157.97	6.844%	$168.7815	$168.78	$168.80	$168.80
Purchase #6	$77.28	4.451%	$80.7197	$80.72	$80.70	$80.70
Purchase #7	$227.77	10.538%	$251.7724	$251.77	$251.75	$251.80
7 purchase totals =	$824.41		$896.1639	$896.16	$896.10	$896.20