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	$233.45	4.619%	$244.2331	$244.23	$244.25	$244.20
Purchase #2	$197.68	10.516%	$218.468	$218.47	$218.45	$218.50
Purchase #3	$136.52	6.669%	$145.6245	$145.62	$145.60	$145.60
Purchase #4	$79.46	8.128%	$85.9185	$85.92	$85.90	$85.90
Purchase #5	$98.45	7.793%	$106.1222	$106.12	$106.10	$106.10
Purchase #6	$69.35	3.271%	$71.6184	$71.62	$71.60	$71.60
Purchase #7	$230.65	10.661%	$255.2396	$255.24	$255.25	$255.20
7 purchase totals =	$1,045.56		$1,127.2243	$1,127.22	$1,127.15	$1,127.10