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	$47.30	12.506%	$53.2153	$53.22	$53.20	$53.20
Purchase #2	$150.96	6.439%	$160.6803	$160.68	$160.70	$160.70
Purchase #3	$221.74	10.392%	$244.7832	$244.78	$244.80	$244.80
Purchase #4	$208.31	6.750%	$222.3709	$222.37	$222.35	$222.40
Purchase #5	$38.53	9.731%	$42.2794	$42.28	$42.30	$42.30
Purchase #6	$55.66	6.820%	$59.456	$59.46	$59.45	$59.50
Purchase #7	$40.41	12.604%	$45.5033	$45.50	$45.50	$45.50
7 purchase totals =	$762.91		$828.2884	$828.29	$828.30	$828.40