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	$204.93	5.337%	$215.8671	$215.87	$215.85	$215.90
Purchase #2	$168.46	13.819%	$191.7395	$191.74	$191.75	$191.70
Purchase #3	$176.59	7.273%	$189.4334	$189.43	$189.45	$189.40
Purchase #4	$250.43	13.650%	$284.6137	$284.61	$284.60	$284.60
Purchase #5	$54.81	5.703%	$57.9358	$57.94	$57.95	$57.90
Purchase #6	$35.98	4.540%	$37.6135	$37.61	$37.60	$37.60
Purchase #7	$32.29	12.865%	$36.4441	$36.44	$36.45	$36.40
7 purchase totals =	$923.49		$1,013.6471	$1,013.64	$1,013.65	$1,013.50