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	$177.83	7.599%	$191.3433	$191.34	$191.35	$191.30
Purchase #2	$90.33	10.149%	$99.4976	$99.50	$99.50	$99.50
Purchase #3	$49.97	11.827%	$55.88	$55.88	$55.90	$55.90
Purchase #4	$203.95	4.580%	$213.2909	$213.29	$213.30	$213.30
Purchase #5	$127.58	7.275%	$136.8614	$136.86	$136.85	$136.90
Purchase #6	$158.56	9.848%	$174.175	$174.18	$174.20	$174.20
Purchase #7	$74.67	8.244%	$80.8258	$80.83	$80.85	$80.80
7 purchase totals =	$882.89		$951.8740	$951.88	$951.95	$951.90