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	$220.73	11.384%	$245.8579	$245.86	$245.85	$245.90
Purchase #2	$149.76	11.543%	$167.0468	$167.05	$167.05	$167.00
Purchase #3	$119.31	3.232%	$123.1661	$123.17	$123.15	$123.20
Purchase #4	$148.85	7.404%	$159.8709	$159.87	$159.85	$159.90
Purchase #5	$85.33	11.557%	$95.1916	$95.19	$95.20	$95.20
Purchase #6	$28.37	12.197%	$31.8303	$31.83	$31.85	$31.80
Purchase #7	$105.85	5.622%	$111.8009	$111.80	$111.80	$111.80
7 purchase totals =	$858.20		$934.7645	$934.77	$934.75	$934.80