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	$193.88	3.558%	$200.7783	$200.78	$200.80	$200.80
Purchase #2	$83.86	7.721%	$90.3348	$90.33	$90.35	$90.30
Purchase #3	$67.59	12.839%	$76.2679	$76.27	$76.25	$76.30
Purchase #4	$172.80	7.319%	$185.4472	$185.45	$185.45	$185.40
Purchase #5	$171.65	13.871%	$195.4596	$195.46	$195.45	$195.50
Purchase #6	$148.57	13.269%	$168.2838	$168.28	$168.30	$168.30
Purchase #7	$38.87	4.785%	$40.7299	$40.73	$40.75	$40.70
7 purchase totals =	$877.22		$957.3015	$957.30	$957.35	$957.30