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	$130.65	10.513%	$144.3852	$144.39	$144.40	$144.40
Purchase #2	$171.52	5.418%	$180.813	$180.81	$180.80	$180.80
Purchase #3	$56.73	9.843%	$62.3139	$62.31	$62.30	$62.30
Purchase #4	$64.46	12.761%	$72.6857	$72.69	$72.70	$72.70
Purchase #5	$155.35	8.513%	$168.5749	$168.57	$168.55	$168.60
Purchase #6	$41.84	8.698%	$45.4792	$45.48	$45.50	$45.50
Purchase #7	$243.54	11.677%	$271.9782	$271.98	$272.00	$272.00
7 purchase totals =	$864.09		$946.2301	$946.23	$946.25	$946.30