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	$13.89	9.646%	$15.2298	$15.23	$15.25	$15.20
Purchase #2	$60.78	5.196%	$63.9381	$63.94	$63.95	$63.90
Purchase #3	$78.56	5.871%	$83.1723	$83.17	$83.15	$83.20
Purchase #4	$62.35	5.121%	$65.5429	$65.54	$65.55	$65.50
Purchase #5	$15.91	9.445%	$17.4127	$17.41	$17.40	$17.40
Purchase #6	$27.27	5.362%	$28.7322	$28.73	$28.75	$28.70
Purchase #7	$152.32	4.603%	$159.3313	$159.33	$159.35	$159.30
7 purchase totals =	$411.08		$433.3593	$433.35	$433.40	$433.20