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	$134.58	11.573%	$150.1549	$150.15	$150.15	$150.20
Purchase #2	$56.53	10.233%	$62.3147	$62.31	$62.30	$62.30
Purchase #3	$144.31	11.130%	$160.3717	$160.37	$160.35	$160.40
Purchase #4	$225.41	13.282%	$255.349	$255.35	$255.35	$255.30
Purchase #5	$138.70	10.224%	$152.8807	$152.88	$152.90	$152.90
Purchase #6	$134.77	5.337%	$141.9627	$141.96	$141.95	$142.00
Purchase #7	$55.31	7.415%	$59.4112	$59.41	$59.40	$59.40
7 purchase totals =	$889.61		$982.4449	$982.43	$982.40	$982.50