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	$45.90	9.653%	$50.3307	$50.33	$50.35	$50.30
Purchase #2	$11.32	5.453%	$11.9373	$11.94	$11.95	$11.90
Purchase #3	$31.97	4.181%	$33.3067	$33.31	$33.30	$33.30
Purchase #4	$224.31	5.134%	$235.8261	$235.83	$235.85	$235.80
Purchase #5	$17.84	5.639%	$18.846	$18.85	$18.85	$18.80
Purchase #6	$80.88	13.334%	$91.6645	$91.66	$91.65	$91.70
Purchase #7	$170.98	8.723%	$185.8946	$185.89	$185.90	$185.90
7 purchase totals =	$583.20		$627.8059	$627.81	$627.85	$627.70