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	$189.27	13.238%	$214.3256	$214.33	$214.35	$214.30
Purchase #2	$112.46	10.223%	$123.9568	$123.96	$123.95	$124.00
Purchase #3	$183.88	8.500%	$199.5098	$199.51	$199.50	$199.50
Purchase #4	$89.74	12.696%	$101.1334	$101.13	$101.15	$101.10
Purchase #5	$24.33	11.587%	$27.1491	$27.15	$27.15	$27.10
Purchase #6	$181.79	4.707%	$190.3469	$190.35	$190.35	$190.30
Purchase #7	$244.48	5.700%	$258.4154	$258.42	$258.40	$258.40
7 purchase totals =	$1,025.95		$1,114.8370	$1,114.85	$1,114.85	$1,114.70