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	$216.40	8.313%	$234.3893	$234.39	$234.40	$234.40
Purchase #2	$117.71	10.157%	$129.6658	$129.67	$129.65	$129.70
Purchase #3	$206.35	3.676%	$213.9354	$213.94	$213.95	$213.90
Purchase #4	$38.46	6.122%	$40.8145	$40.81	$40.80	$40.80
Purchase #5	$85.69	4.816%	$89.8168	$89.82	$89.80	$89.80
Purchase #6	$160.93	6.281%	$171.038	$171.04	$171.05	$171.00
Purchase #7	$119.47	4.494%	$124.839	$124.84	$124.85	$124.80
7 purchase totals =	$945.01		$1,004.4988	$1,004.51	$1,004.50	$1,004.40