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	$248.48	9.434%	$271.9216	$271.92	$271.90	$271.90
Purchase #2	$197.39	12.342%	$221.7519	$221.75	$221.75	$221.80
Purchase #3	$56.96	4.562%	$59.5585	$59.56	$59.55	$59.60
Purchase #4	$100.39	6.356%	$106.7708	$106.77	$106.75	$106.80
Purchase #5	$79.42	5.649%	$83.9064	$83.91	$83.90	$83.90
Purchase #6	$239.28	12.627%	$269.4939	$269.49	$269.50	$269.50
Purchase #7	$43.65	6.453%	$46.4667	$46.47	$46.45	$46.50
7 purchase totals =	$965.57		$1,059.8698	$1,059.87	$1,059.80	$1,060.00