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	$165.93	3.563%	$171.8421	$171.84	$171.85	$171.80
Purchase #2	$225.72	11.138%	$250.8607	$250.86	$250.85	$250.90
Purchase #3	$177.50	4.254%	$185.0509	$185.05	$185.05	$185.10
Purchase #4	$51.97	8.749%	$56.5169	$56.52	$56.50	$56.50
Purchase #5	$75.53	8.412%	$81.8836	$81.88	$81.90	$81.90
Purchase #6	$244.56	8.542%	$265.4503	$265.45	$265.45	$265.50
Purchase #7	$52.30	7.436%	$56.189	$56.19	$56.20	$56.20
7 purchase totals =	$993.51		$1,067.7935	$1,067.79	$1,067.80	$1,067.90