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	$162.43	3.714%	$168.4627	$168.46	$168.45	$168.50
Purchase #2	$50.79	8.625%	$55.1706	$55.17	$55.15	$55.20
Purchase #3	$170.52	9.197%	$186.2027	$186.20	$186.20	$186.20
Purchase #4	$157.63	4.421%	$164.5988	$164.60	$164.60	$164.60
Purchase #5	$207.35	13.499%	$235.3402	$235.34	$235.35	$235.30
Purchase #6	$133.89	9.419%	$146.5011	$146.50	$146.50	$146.50
Purchase #7	$233.43	9.392%	$255.3537	$255.35	$255.35	$255.40
7 purchase totals =	$1,116.04		$1,211.6298	$1,211.62	$1,211.60	$1,211.70