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	$66.74	11.667%	$74.5266	$74.53	$74.55	$74.50
Purchase #2	$171.56	11.857%	$191.9019	$191.90	$191.90	$191.90
Purchase #3	$130.28	5.412%	$137.3308	$137.33	$137.35	$137.30
Purchase #4	$11.35	4.851%	$11.9006	$11.90	$11.90	$11.90
Purchase #5	$63.33	5.259%	$66.6605	$66.66	$66.65	$66.70
Purchase #6	$70.37	11.622%	$78.5484	$78.55	$78.55	$78.50
Purchase #7	$147.36	13.685%	$167.5262	$167.53	$167.55	$167.50
7 purchase totals =	$660.99		$728.3950	$728.40	$728.45	$728.30