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	$75.56	10.646%	$83.6041	$83.60	$83.60	$83.60
Purchase #2	$160.47	9.617%	$175.9024	$175.90	$175.90	$175.90
Purchase #3	$110.83	11.485%	$123.5588	$123.56	$123.55	$123.60
Purchase #4	$137.31	13.169%	$155.3924	$155.39	$155.40	$155.40
Purchase #5	$88.56	12.783%	$99.8806	$99.88	$99.90	$99.90
Purchase #6	$82.72	12.131%	$92.7548	$92.75	$92.75	$92.80
Purchase #7	$46.31	4.773%	$48.5204	$48.52	$48.50	$48.50
7 purchase totals =	$701.76		$779.6135	$779.60	$779.60	$779.70