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	$185.57	3.592%	$192.2357	$192.24	$192.25	$192.20
Purchase #2	$75.33	6.256%	$80.0426	$80.04	$80.05	$80.00
Purchase #3	$55.71	3.395%	$57.6014	$57.60	$57.60	$57.60
Purchase #4	$228.33	4.396%	$238.3674	$238.37	$238.35	$238.40
Purchase #5	$236.29	10.764%	$261.7243	$261.72	$261.70	$261.70
Purchase #6	$123.55	10.386%	$136.3819	$136.38	$136.40	$136.40
Purchase #7	$157.89	13.417%	$179.0741	$179.07	$179.05	$179.10
7 purchase totals =	$1,062.67		$1,145.4274	$1,145.42	$1,145.40	$1,145.40