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	$46.46	12.471%	$52.254	$52.25	$52.25	$52.30
Purchase #2	$10.65	10.400%	$11.7576	$11.76	$11.75	$11.80
Purchase #3	$98.34	11.502%	$109.6511	$109.65	$109.65	$109.70
Purchase #4	$58.48	9.628%	$64.1105	$64.11	$64.10	$64.10
Purchase #5	$90.50	13.847%	$103.0315	$103.03	$103.05	$103.00
Purchase #6	$165.82	12.871%	$187.1627	$187.16	$187.15	$187.20
Purchase #7	$77.76	3.603%	$80.5617	$80.56	$80.55	$80.60
7 purchase totals =	$548.01		$608.5291	$608.52	$608.50	$608.70