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	$235.52	12.117%	$264.058	$264.06	$264.05	$264.10
Purchase #2	$149.91	12.373%	$168.4584	$168.46	$168.45	$168.50
Purchase #3	$138.57	11.616%	$154.6663	$154.67	$154.65	$154.70
Purchase #4	$100.33	12.523%	$112.8943	$112.89	$112.90	$112.90
Purchase #5	$178.77	8.669%	$194.2676	$194.27	$194.25	$194.30
Purchase #6	$48.29	3.810%	$50.1298	$50.13	$50.15	$50.10
Purchase #7	$105.79	13.856%	$120.4483	$120.45	$120.45	$120.40
7 purchase totals =	$957.18		$1,064.9227	$1,064.93	$1,064.90	$1,065.00