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	$70.90	7.246%	$76.0374	$76.04	$76.05	$76.00
Purchase #2	$42.85	6.481%	$45.6271	$45.63	$45.65	$45.60
Purchase #3	$132.70	10.499%	$146.6322	$146.63	$146.65	$146.60
Purchase #4	$168.70	3.822%	$175.1477	$175.15	$175.15	$175.10
Purchase #5	$156.54	9.419%	$171.2845	$171.28	$171.30	$171.30
Purchase #6	$41.98	8.641%	$45.6075	$45.61	$45.60	$45.60
Purchase #7	$229.85	12.350%	$258.2365	$258.24	$258.25	$258.20
7 purchase totals =	$843.52		$918.5729	$918.58	$918.65	$918.40