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	$70.45	3.231%	$72.7262	$72.73	$72.75	$72.70
Purchase #2	$166.42	11.778%	$186.0209	$186.02	$186.00	$186.00
Purchase #3	$202.32	3.299%	$208.9945	$208.99	$209.00	$209.00
Purchase #4	$224.26	8.433%	$243.1718	$243.17	$243.15	$243.20
Purchase #5	$95.45	5.402%	$100.6062	$100.61	$100.60	$100.60
Purchase #6	$80.82	13.471%	$91.7073	$91.71	$91.70	$91.70
Purchase #7	$101.87	9.128%	$111.1687	$111.17	$111.15	$111.20
7 purchase totals =	$941.59		$1,014.3956	$1,014.40	$1,014.35	$1,014.40