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	$149.27	5.770%	$157.8829	$157.88	$157.90	$157.90
Purchase #2	$114.87	3.151%	$118.4896	$118.49	$118.50	$118.50
Purchase #3	$37.35	13.721%	$42.4748	$42.47	$42.45	$42.50
Purchase #4	$78.25	7.490%	$84.1109	$84.11	$84.10	$84.10
Purchase #5	$209.40	6.436%	$222.877	$222.88	$222.90	$222.90
Purchase #6	$244.73	7.408%	$262.8596	$262.86	$262.85	$262.90
Purchase #7	$82.76	3.602%	$85.741	$85.74	$85.75	$85.70
7 purchase totals =	$916.63		$974.4358	$974.43	$974.45	$974.50