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	$151.66	9.236%	$165.6673	$165.67	$165.65	$165.70
Purchase #2	$156.31	3.673%	$162.0513	$162.05	$162.05	$162.10
Purchase #3	$72.30	3.594%	$74.8985	$74.90	$74.90	$74.90
Purchase #4	$247.34	5.168%	$260.1225	$260.12	$260.10	$260.10
Purchase #5	$70.84	13.766%	$80.5918	$80.59	$80.60	$80.60
Purchase #6	$155.56	13.386%	$176.3833	$176.38	$176.40	$176.40
Purchase #7	$118.55	4.233%	$123.5682	$123.57	$123.55	$123.60
7 purchase totals =	$972.56		$1,043.2829	$1,043.28	$1,043.25	$1,043.40