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	$42.88	10.364%	$47.3241	$47.32	$47.30	$47.30
Purchase #2	$77.49	13.252%	$87.759	$87.76	$87.75	$87.80
Purchase #3	$50.38	3.666%	$52.2269	$52.23	$52.25	$52.20
Purchase #4	$131.71	7.558%	$141.6646	$141.66	$141.65	$141.70
Purchase #5	$73.59	4.790%	$77.115	$77.12	$77.10	$77.10
Purchase #6	$29.28	8.766%	$31.8467	$31.85	$31.85	$31.80
Purchase #7	$216.79	5.754%	$229.2641	$229.26	$229.25	$229.30
7 purchase totals =	$622.12		$667.2004	$667.20	$667.15	$667.20