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	$35.67	5.519%	$37.6386	$37.64	$37.65	$37.60
Purchase #2	$214.72	9.179%	$234.4291	$234.43	$234.45	$234.40
Purchase #3	$85.78	5.867%	$90.8127	$90.81	$90.80	$90.80
Purchase #4	$85.61	6.470%	$91.149	$91.15	$91.15	$91.10
Purchase #5	$236.40	9.742%	$259.4301	$259.43	$259.45	$259.40
Purchase #6	$70.55	7.484%	$75.83	$75.83	$75.85	$75.80
Purchase #7	$171.54	13.762%	$195.1473	$195.15	$195.15	$195.10
7 purchase totals =	$900.27		$984.4368	$984.44	$984.50	$984.20