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	$216.35	5.344%	$227.9117	$227.91	$227.90	$227.90
Purchase #2	$41.80	4.489%	$43.6764	$43.68	$43.70	$43.70
Purchase #3	$149.51	4.652%	$156.4652	$156.47	$156.45	$156.50
Purchase #4	$28.65	6.587%	$30.5372	$30.54	$30.55	$30.50
Purchase #5	$199.43	12.147%	$223.6548	$223.65	$223.65	$223.70
Purchase #6	$178.66	10.136%	$196.769	$196.77	$196.75	$196.80
Purchase #7	$90.68	4.143%	$94.4369	$94.44	$94.45	$94.40
7 purchase totals =	$905.08		$973.4512	$973.46	$973.45	$973.50