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	$72.32	4.405%	$75.5057	$75.51	$75.50	$75.50
Purchase #2	$139.31	13.721%	$158.4247	$158.42	$158.40	$158.40
Purchase #3	$184.54	12.325%	$207.2846	$207.28	$207.30	$207.30
Purchase #4	$153.69	8.273%	$166.4048	$166.40	$166.40	$166.40
Purchase #5	$143.56	10.483%	$158.6094	$158.61	$158.60	$158.60
Purchase #6	$161.86	4.666%	$169.4124	$169.41	$169.40	$169.40
Purchase #7	$245.33	4.429%	$256.1957	$256.20	$256.20	$256.20
7 purchase totals =	$1,100.61		$1,191.8373	$1,191.83	$1,191.80	$1,191.80