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	$215.94	12.308%	$242.5179	$242.52	$242.50	$242.50
Purchase #2	$90.78	8.575%	$98.5644	$98.56	$98.55	$98.60
Purchase #3	$24.76	7.379%	$26.587	$26.59	$26.60	$26.60
Purchase #4	$229.52	3.870%	$238.4024	$238.40	$238.40	$238.40
Purchase #5	$205.28	12.401%	$230.7368	$230.74	$230.75	$230.70
Purchase #6	$71.65	9.438%	$78.4123	$78.41	$78.40	$78.40
Purchase #7	$166.38	7.639%	$179.0898	$179.09	$179.10	$179.10
7 purchase totals =	$1,004.31		$1,094.3106	$1,094.31	$1,094.30	$1,094.30