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	$14.96	3.350%	$15.4612	$15.46	$15.45	$15.50
Purchase #2	$160.78	6.444%	$171.1407	$171.14	$171.15	$171.10
Purchase #3	$29.37	13.328%	$33.2844	$33.28	$33.30	$33.30
Purchase #4	$80.89	6.201%	$85.906	$85.91	$85.90	$85.90
Purchase #5	$170.76	11.859%	$191.0104	$191.01	$191.00	$191.00
Purchase #6	$95.28	12.103%	$106.8117	$106.81	$106.80	$106.80
Purchase #7	$24.90	3.321%	$25.7269	$25.73	$25.75	$25.70
7 purchase totals =	$576.94		$629.3413	$629.34	$629.35	$629.30