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	$175.86	4.715%	$184.1518	$184.15	$184.15	$184.20
Purchase #2	$185.31	6.828%	$197.963	$197.96	$197.95	$198.00
Purchase #3	$200.58	5.868%	$212.35	$212.35	$212.35	$212.40
Purchase #4	$13.62	6.861%	$14.5545	$14.55	$14.55	$14.60
Purchase #5	$123.54	3.250%	$127.5551	$127.56	$127.55	$127.60
Purchase #6	$170.90	12.496%	$192.2557	$192.26	$192.25	$192.30
Purchase #7	$82.52	10.838%	$91.4635	$91.46	$91.45	$91.50
7 purchase totals =	$952.33		$1,020.2936	$1,020.29	$1,020.25	$1,020.60