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	$33.69	10.857%	$37.3477	$37.35	$37.35	$37.30
Purchase #2	$134.64	8.164%	$145.632	$145.63	$145.65	$145.60
Purchase #3	$216.73	7.338%	$232.6336	$232.63	$232.65	$232.60
Purchase #4	$247.61	3.630%	$256.5982	$256.60	$256.60	$256.60
Purchase #5	$58.79	4.408%	$61.3815	$61.38	$61.40	$61.40
Purchase #6	$80.88	11.387%	$90.0898	$90.09	$90.10	$90.10
Purchase #7	$170.26	13.171%	$192.6849	$192.68	$192.70	$192.70
7 purchase totals =	$942.60		$1,016.3677	$1,016.36	$1,016.45	$1,016.30