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	$30.46	4.596%	$31.8599	$31.86	$31.85	$31.90
Purchase #2	$198.40	5.581%	$209.4727	$209.47	$209.45	$209.50
Purchase #3	$79.82	3.239%	$82.4054	$82.41	$82.40	$82.40
Purchase #4	$80.57	5.633%	$85.1085	$85.11	$85.10	$85.10
Purchase #5	$33.89	6.428%	$36.0684	$36.07	$36.05	$36.10
Purchase #6	$86.94	5.674%	$91.873	$91.87	$91.85	$91.90
Purchase #7	$206.94	5.480%	$218.2803	$218.28	$218.30	$218.30
7 purchase totals =	$717.02		$755.0682	$755.07	$755.00	$755.20