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	$52.36	3.522%	$54.2041	$54.20	$54.20	$54.20
Purchase #2	$136.83	3.181%	$141.1826	$141.18	$141.20	$141.20
Purchase #3	$100.86	13.183%	$114.1564	$114.16	$114.15	$114.20
Purchase #4	$140.85	12.695%	$158.7309	$158.73	$158.75	$158.70
Purchase #5	$69.29	11.362%	$77.1627	$77.16	$77.15	$77.20
Purchase #6	$215.69	3.132%	$222.4454	$222.45	$222.45	$222.40
Purchase #7	$155.40	10.369%	$171.5134	$171.51	$171.50	$171.50
7 purchase totals =	$871.28		$939.3955	$939.39	$939.40	$939.40