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	$51.33	5.824%	$54.3195	$54.32	$54.30	$54.30
Purchase #2	$61.51	13.312%	$69.6982	$69.70	$69.70	$69.70
Purchase #3	$205.39	10.463%	$226.88	$226.88	$226.90	$226.90
Purchase #4	$44.89	12.419%	$50.4649	$50.46	$50.45	$50.50
Purchase #5	$132.50	12.370%	$148.8903	$148.89	$148.90	$148.90
Purchase #6	$211.97	5.164%	$222.9161	$222.92	$222.90	$222.90
Purchase #7	$72.37	4.459%	$75.597	$75.60	$75.60	$75.60
7 purchase totals =	$779.96		$848.7660	$848.77	$848.75	$848.80