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	$196.26	12.485%	$220.7631	$220.76	$220.75	$220.80
Purchase #2	$38.35	4.204%	$39.9622	$39.96	$39.95	$40.00
Purchase #3	$87.96	12.817%	$99.2338	$99.23	$99.25	$99.20
Purchase #4	$128.82	4.262%	$134.3103	$134.31	$134.30	$134.30
Purchase #5	$5.62	13.666%	$6.388	$6.39	$6.40	$6.40
Purchase #6	$131.54	7.829%	$141.8383	$141.84	$141.85	$141.80
Purchase #7	$119.63	3.616%	$123.9558	$123.96	$123.95	$124.00
7 purchase totals =	$708.18		$766.4515	$766.45	$766.45	$766.50