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	$165.45	6.308%	$175.8866	$175.89	$175.90	$175.90
Purchase #2	$151.94	11.318%	$169.1366	$169.14	$169.15	$169.10
Purchase #3	$236.34	13.411%	$268.0356	$268.04	$268.05	$268.00
Purchase #4	$84.39	7.712%	$90.8982	$90.90	$90.90	$90.90
Purchase #5	$100.29	3.121%	$103.4201	$103.42	$103.40	$103.40
Purchase #6	$144.56	10.558%	$159.8226	$159.82	$159.80	$159.80
Purchase #7	$211.72	6.620%	$225.7359	$225.74	$225.75	$225.70
7 purchase totals =	$1,094.69		$1,192.9356	$1,192.95	$1,192.95	$1,192.80