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	$245.56	5.619%	$259.358	$259.36	$259.35	$259.40
Purchase #2	$99.52	4.355%	$103.8541	$103.85	$103.85	$103.90
Purchase #3	$127.95	13.681%	$145.4548	$145.45	$145.45	$145.50
Purchase #4	$153.39	12.168%	$172.0545	$172.05	$172.05	$172.10
Purchase #5	$33.78	4.634%	$35.3454	$35.35	$35.35	$35.30
Purchase #6	$234.35	5.315%	$246.8057	$246.81	$246.80	$246.80
Purchase #7	$121.35	5.443%	$127.9551	$127.96	$127.95	$128.00
7 purchase totals =	$1,015.90		$1,090.8276	$1,090.83	$1,090.80	$1,091.00