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	$79.71	7.770%	$85.9035	$85.90	$85.90	$85.90
Purchase #2	$148.73	6.772%	$158.802	$158.80	$158.80	$158.80
Purchase #3	$155.57	10.128%	$171.3261	$171.33	$171.35	$171.30
Purchase #4	$121.31	12.705%	$136.7224	$136.72	$136.70	$136.70
Purchase #5	$187.45	12.776%	$211.3986	$211.40	$211.40	$211.40
Purchase #6	$211.26	7.810%	$227.7594	$227.76	$227.75	$227.80
Purchase #7	$21.77	12.693%	$24.5333	$24.53	$24.55	$24.50
7 purchase totals =	$925.80		$1,016.4453	$1,016.44	$1,016.45	$1,016.40