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	$185.48	4.302%	$193.4593	$193.46	$193.45	$193.50
Purchase #2	$139.48	6.328%	$148.3063	$148.31	$148.30	$148.30
Purchase #3	$62.89	7.349%	$67.5118	$67.51	$67.50	$67.50
Purchase #4	$76.53	5.474%	$80.7193	$80.72	$80.70	$80.70
Purchase #5	$90.50	3.466%	$93.6367	$93.64	$93.65	$93.60
Purchase #6	$244.25	11.304%	$271.86	$271.86	$271.85	$271.90
Purchase #7	$231.91	13.711%	$263.7072	$263.71	$263.70	$263.70
7 purchase totals =	$1,031.04		$1,119.2006	$1,119.21	$1,119.15	$1,119.20