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	$123.89	13.494%	$140.6077	$140.61	$140.60	$140.60
Purchase #2	$158.60	5.144%	$166.7584	$166.76	$166.75	$166.80
Purchase #3	$71.64	7.361%	$76.9134	$76.91	$76.90	$76.90
Purchase #4	$124.46	10.608%	$137.6627	$137.66	$137.65	$137.70
Purchase #5	$95.39	5.170%	$100.3217	$100.32	$100.30	$100.30
Purchase #6	$220.92	11.108%	$245.4598	$245.46	$245.45	$245.50
Purchase #7	$58.81	9.295%	$64.2764	$64.28	$64.30	$64.30
7 purchase totals =	$853.71		$932.0001	$932.00	$931.95	$932.10