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	$65.25	9.578%	$71.4996	$71.50	$71.50	$71.50
Purchase #2	$232.89	6.288%	$247.5341	$247.53	$247.55	$247.50
Purchase #3	$104.71	7.550%	$112.6156	$112.62	$112.60	$112.60
Purchase #4	$104.55	12.572%	$117.694	$117.69	$117.70	$117.70
Purchase #5	$18.30	13.444%	$20.7603	$20.76	$20.75	$20.80
Purchase #6	$192.32	8.428%	$208.5287	$208.53	$208.55	$208.50
Purchase #7	$155.87	8.744%	$169.4993	$169.50	$169.50	$169.50
7 purchase totals =	$873.89		$948.1316	$948.13	$948.15	$948.10