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	$92.85	13.403%	$105.2947	$105.29	$105.30	$105.30
Purchase #2	$228.73	3.397%	$236.5	$236.50	$236.50	$236.50
Purchase #3	$152.66	13.508%	$173.2813	$173.28	$173.30	$173.30
Purchase #4	$92.79	11.151%	$103.137	$103.14	$103.15	$103.10
Purchase #5	$225.27	13.328%	$255.294	$255.29	$255.30	$255.30
Purchase #6	$45.28	5.473%	$47.7582	$47.76	$47.75	$47.80
Purchase #7	$63.88	12.797%	$72.0547	$72.05	$72.05	$72.10
7 purchase totals =	$901.46		$993.3199	$993.31	$993.35	$993.40