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	$70.41	3.172%	$72.6434	$72.64	$72.65	$72.60
Purchase #2	$33.47	7.117%	$35.8521	$35.85	$35.85	$35.90
Purchase #3	$93.58	5.168%	$98.4162	$98.42	$98.40	$98.40
Purchase #4	$248.52	10.382%	$274.3213	$274.32	$274.30	$274.30
Purchase #5	$222.56	10.290%	$245.4614	$245.46	$245.45	$245.50
Purchase #6	$148.63	12.123%	$166.6484	$166.65	$166.65	$166.60
Purchase #7	$107.26	9.477%	$117.425	$117.43	$117.45	$117.40
7 purchase totals =	$924.43		$1,010.7678	$1,010.77	$1,010.75	$1,010.70