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	$220.45	10.610%	$243.8397	$243.84	$243.85	$243.80
Purchase #2	$41.76	13.147%	$47.2502	$47.25	$47.25	$47.30
Purchase #3	$50.72	9.719%	$55.6495	$55.65	$55.65	$55.60
Purchase #4	$39.41	6.374%	$41.922	$41.92	$41.90	$41.90
Purchase #5	$176.47	8.701%	$191.8247	$191.82	$191.80	$191.80
Purchase #6	$85.27	11.562%	$95.1289	$95.13	$95.15	$95.10
Purchase #7	$200.39	12.610%	$225.6592	$225.66	$225.65	$225.70
7 purchase totals =	$814.47		$901.2742	$901.27	$901.25	$901.20