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	$124.94	5.608%	$131.9466	$131.95	$131.95	$131.90
Purchase #2	$51.42	4.139%	$53.5483	$53.55	$53.55	$53.50
Purchase #3	$218.74	12.412%	$245.89	$245.89	$245.90	$245.90
Purchase #4	$209.68	5.827%	$221.8981	$221.90	$221.90	$221.90
Purchase #5	$76.94	4.847%	$80.6693	$80.67	$80.65	$80.70
Purchase #6	$69.33	11.860%	$77.5525	$77.55	$77.55	$77.60
Purchase #7	$111.45	10.163%	$122.7767	$122.78	$122.80	$122.80
7 purchase totals =	$862.50		$934.2815	$934.29	$934.30	$934.30