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	$237.30	9.630%	$260.152	$260.15	$260.15	$260.20
Purchase #2	$119.30	8.802%	$129.8008	$129.80	$129.80	$129.80
Purchase #3	$148.32	11.832%	$165.8692	$165.87	$165.85	$165.90
Purchase #4	$106.64	4.843%	$111.8046	$111.80	$111.80	$111.80
Purchase #5	$20.27	4.182%	$21.1177	$21.12	$21.10	$21.10
Purchase #6	$238.90	9.589%	$261.8081	$261.81	$261.80	$261.80
Purchase #7	$75.25	11.385%	$83.8172	$83.82	$83.80	$83.80
7 purchase totals =	$945.98		$1,034.3696	$1,034.37	$1,034.30	$1,034.40