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	$151.72	8.261%	$164.2536	$164.25	$164.25	$164.30
Purchase #2	$180.64	4.584%	$188.9205	$188.92	$188.90	$188.90
Purchase #3	$74.87	4.709%	$78.3956	$78.40	$78.40	$78.40
Purchase #4	$159.88	9.669%	$175.3388	$175.34	$175.35	$175.30
Purchase #5	$220.94	4.599%	$231.101	$231.10	$231.10	$231.10
Purchase #6	$66.29	10.412%	$73.1921	$73.19	$73.20	$73.20
Purchase #7	$150.82	7.108%	$161.5403	$161.54	$161.55	$161.50
7 purchase totals =	$1,005.16		$1,072.7419	$1,072.74	$1,072.75	$1,072.70