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	$153.87	13.516%	$174.6671	$174.67	$174.65	$174.70
Purchase #2	$231.52	5.245%	$243.6632	$243.66	$243.65	$243.70
Purchase #3	$186.59	13.170%	$211.1639	$211.16	$211.15	$211.20
Purchase #4	$246.48	13.652%	$280.1294	$280.13	$280.15	$280.10
Purchase #5	$183.75	11.764%	$205.3664	$205.37	$205.35	$205.40
Purchase #6	$63.79	13.663%	$72.5056	$72.51	$72.50	$72.50
Purchase #7	$69.91	11.709%	$78.0958	$78.10	$78.10	$78.10
7 purchase totals =	$1,135.91		$1,265.5914	$1,265.60	$1,265.55	$1,265.70