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	$246.61	7.111%	$264.1464	$264.15	$264.15	$264.10
Purchase #2	$179.74	4.593%	$187.9955	$188.00	$188.00	$188.00
Purchase #3	$99.89	5.723%	$105.6067	$105.61	$105.60	$105.60
Purchase #4	$178.76	9.691%	$196.0836	$196.08	$196.10	$196.10
Purchase #5	$105.26	12.574%	$118.4954	$118.50	$118.50	$118.50
Purchase #6	$246.69	12.124%	$276.5987	$276.60	$276.60	$276.60
Purchase #7	$151.31	5.170%	$159.1327	$159.13	$159.15	$159.10
7 purchase totals =	$1,208.26		$1,308.0590	$1,308.07	$1,308.10	$1,308.00