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	$176.77	7.747%	$190.4644	$190.46	$190.45	$190.50
Purchase #2	$88.40	11.300%	$98.3892	$98.39	$98.40	$98.40
Purchase #3	$235.57	4.216%	$245.5016	$245.50	$245.50	$245.50
Purchase #4	$90.82	4.529%	$94.9332	$94.93	$94.95	$94.90
Purchase #5	$79.33	6.538%	$84.5166	$84.52	$84.50	$84.50
Purchase #6	$42.39	7.433%	$45.5408	$45.54	$45.55	$45.50
Purchase #7	$172.93	11.133%	$192.1823	$192.18	$192.20	$192.20
7 purchase totals =	$886.21		$951.5281	$951.52	$951.55	$951.50