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	$187.45	10.128%	$206.4349	$206.43	$206.45	$206.40
Purchase #2	$248.33	4.437%	$259.3484	$259.35	$259.35	$259.30
Purchase #3	$111.86	4.317%	$116.689	$116.69	$116.70	$116.70
Purchase #4	$35.78	12.113%	$40.114	$40.11	$40.10	$40.10
Purchase #5	$142.53	12.115%	$159.7975	$159.80	$159.80	$159.80
Purchase #6	$173.33	4.250%	$180.6965	$180.70	$180.70	$180.70
Purchase #7	$95.25	5.737%	$100.7145	$100.71	$100.70	$100.70
7 purchase totals =	$994.53		$1,063.7948	$1,063.79	$1,063.80	$1,063.70