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	$237.33	6.685%	$253.1955	$253.20	$253.20	$253.20
Purchase #2	$85.95	5.307%	$90.5114	$90.51	$90.50	$90.50
Purchase #3	$166.30	3.681%	$172.4215	$172.42	$172.40	$172.40
Purchase #4	$25.57	9.758%	$28.0651	$28.07	$28.05	$28.10
Purchase #5	$130.25	8.274%	$141.0269	$141.03	$141.05	$141.00
Purchase #6	$215.32	11.258%	$239.5607	$239.56	$239.55	$239.60
Purchase #7	$111.54	4.121%	$116.1366	$116.14	$116.15	$116.10
7 purchase totals =	$972.26		$1,040.9177	$1,040.93	$1,040.90	$1,040.90