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	$184.38	3.359%	$190.5733	$190.57	$190.55	$190.60
Purchase #2	$88.69	4.654%	$92.8176	$92.82	$92.80	$92.80
Purchase #3	$31.38	5.852%	$33.2164	$33.22	$33.20	$33.20
Purchase #4	$245.39	12.766%	$276.7165	$276.72	$276.70	$276.70
Purchase #5	$56.83	4.827%	$59.5732	$59.57	$59.55	$59.60
Purchase #6	$35.56	9.791%	$39.0417	$39.04	$39.05	$39.00
Purchase #7	$234.81	11.468%	$261.738	$261.74	$261.75	$261.70
7 purchase totals =	$877.04		$953.6767	$953.68	$953.60	$953.60