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	$46.48	13.753%	$52.8724	$52.87	$52.85	$52.90
Purchase #2	$183.83	6.723%	$196.1889	$196.19	$196.20	$196.20
Purchase #3	$117.91	11.164%	$131.0735	$131.07	$131.05	$131.10
Purchase #4	$43.68	6.738%	$46.6232	$46.62	$46.60	$46.60
Purchase #5	$211.51	3.767%	$219.4776	$219.48	$219.50	$219.50
Purchase #6	$125.76	3.266%	$129.8673	$129.87	$129.85	$129.90
Purchase #7	$181.27	10.790%	$200.829	$200.83	$200.85	$200.80
7 purchase totals =	$910.44		$976.9319	$976.93	$976.90	$977.00