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	$17.95	4.344%	$18.7297	$18.73	$18.75	$18.70
Purchase #2	$72.98	11.432%	$81.3231	$81.32	$81.30	$81.30
Purchase #3	$120.96	3.854%	$125.6218	$125.62	$125.60	$125.60
Purchase #4	$185.87	7.830%	$200.4236	$200.42	$200.40	$200.40
Purchase #5	$80.98	5.650%	$85.5554	$85.56	$85.55	$85.60
Purchase #6	$74.82	11.512%	$83.4333	$83.43	$83.45	$83.40
Purchase #7	$220.41	3.227%	$227.5226	$227.52	$227.50	$227.50
7 purchase totals =	$773.97		$822.6095	$822.60	$822.55	$822.50