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	$195.83	4.636%	$204.9087	$204.91	$204.90	$204.90
Purchase #2	$172.78	7.306%	$185.4033	$185.40	$185.40	$185.40
Purchase #3	$181.38	3.507%	$187.741	$187.74	$187.75	$187.70
Purchase #4	$60.68	13.551%	$68.9027	$68.90	$68.90	$68.90
Purchase #5	$82.53	5.844%	$87.3531	$87.35	$87.35	$87.40
Purchase #6	$158.37	13.595%	$179.9004	$179.90	$179.90	$179.90
Purchase #7	$246.56	7.642%	$265.4021	$265.40	$265.40	$265.40
7 purchase totals =	$1,098.13		$1,179.6113	$1,179.60	$1,179.60	$1,179.60