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	$36.35	4.279%	$37.9054	$37.91	$37.90	$37.90
Purchase #2	$220.52	9.683%	$241.873	$241.87	$241.85	$241.90
Purchase #3	$162.86	6.653%	$173.6951	$173.70	$173.70	$173.70
Purchase #4	$93.57	6.202%	$99.3732	$99.37	$99.35	$99.40
Purchase #5	$70.72	10.841%	$78.3868	$78.39	$78.40	$78.40
Purchase #6	$217.68	4.640%	$227.7804	$227.78	$227.80	$227.80
Purchase #7	$22.98	13.236%	$26.0216	$26.02	$26.00	$26.00
7 purchase totals =	$824.68		$885.0355	$885.04	$885.00	$885.10