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	$248.53	6.752%	$265.3107	$265.31	$265.30	$265.30
Purchase #2	$162.56	6.225%	$172.6794	$172.68	$172.70	$172.70
Purchase #3	$44.50	13.719%	$50.605	$50.61	$50.60	$50.60
Purchase #4	$44.75	13.469%	$50.7774	$50.78	$50.80	$50.80
Purchase #5	$143.41	12.317%	$161.0738	$161.07	$161.05	$161.10
Purchase #6	$128.88	6.672%	$137.4789	$137.48	$137.50	$137.50
Purchase #7	$198.63	13.219%	$224.8869	$224.89	$224.90	$224.90
7 purchase totals =	$971.26		$1,062.8121	$1,062.82	$1,062.85	$1,062.90