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	$174.84	7.579%	$188.0911	$188.09	$188.10	$188.10
Purchase #2	$203.79	4.804%	$213.5801	$213.58	$213.60	$213.60
Purchase #3	$103.96	7.360%	$111.6115	$111.61	$111.60	$111.60
Purchase #4	$224.61	8.180%	$242.9831	$242.98	$243.00	$243.00
Purchase #5	$38.80	10.119%	$42.7262	$42.73	$42.75	$42.70
Purchase #6	$56.91	13.828%	$64.7795	$64.78	$64.80	$64.80
Purchase #7	$6.79	8.536%	$7.3696	$7.37	$7.35	$7.40
7 purchase totals =	$809.70		$871.1411	$871.14	$871.20	$871.20