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	$29.81	7.571%	$32.0669	$32.07	$32.05	$32.10
Purchase #2	$43.33	10.134%	$47.7211	$47.72	$47.70	$47.70
Purchase #3	$219.34	5.386%	$231.1537	$231.15	$231.15	$231.20
Purchase #4	$226.81	10.450%	$250.5116	$250.51	$250.50	$250.50
Purchase #5	$36.40	8.347%	$39.4383	$39.44	$39.45	$39.40
Purchase #6	$45.51	10.556%	$50.314	$50.31	$50.30	$50.30
Purchase #7	$115.85	13.211%	$131.1549	$131.15	$131.15	$131.20
7 purchase totals =	$717.05		$782.3605	$782.35	$782.30	$782.40