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	$195.97	10.244%	$216.0452	$216.05	$216.05	$216.00
Purchase #2	$178.71	6.690%	$190.6657	$190.67	$190.65	$190.70
Purchase #3	$36.64	7.226%	$39.2876	$39.29	$39.30	$39.30
Purchase #4	$73.83	5.318%	$77.7563	$77.76	$77.75	$77.80
Purchase #5	$149.61	13.272%	$169.4662	$169.47	$169.45	$169.50
Purchase #6	$79.71	12.452%	$89.6355	$89.64	$89.65	$89.60
Purchase #7	$37.79	13.424%	$42.8629	$42.86	$42.85	$42.90
7 purchase totals =	$752.26		$825.7194	$825.74	$825.70	$825.80