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	$199.69	12.839%	$225.3282	$225.33	$225.35	$225.30
Purchase #2	$205.89	10.397%	$227.2964	$227.30	$227.30	$227.30
Purchase #3	$84.81	12.781%	$95.6496	$95.65	$95.65	$95.60
Purchase #4	$243.90	10.311%	$269.0485	$269.05	$269.05	$269.00
Purchase #5	$85.30	11.243%	$94.8903	$94.89	$94.90	$94.90
Purchase #6	$50.74	4.607%	$53.0776	$53.08	$53.10	$53.10
Purchase #7	$88.96	8.169%	$96.2271	$96.23	$96.25	$96.20
7 purchase totals =	$959.29		$1,061.5177	$1,061.53	$1,061.60	$1,061.40