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	$14.53	10.417%	$16.0436	$16.04	$16.05	$16.00
Purchase #2	$224.46	11.562%	$250.4121	$250.41	$250.40	$250.40
Purchase #3	$227.59	10.700%	$251.9421	$251.94	$251.95	$251.90
Purchase #4	$54.33	8.859%	$59.1431	$59.14	$59.15	$59.10
Purchase #5	$214.77	3.295%	$221.8467	$221.85	$221.85	$221.80
Purchase #6	$82.33	4.308%	$85.8768	$85.88	$85.90	$85.90
Purchase #7	$230.51	6.695%	$245.9426	$245.94	$245.95	$245.90
7 purchase totals =	$1,048.52		$1,131.2070	$1,131.20	$1,131.25	$1,131.00