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	$69.37	4.389%	$72.4146	$72.41	$72.40	$72.40
Purchase #2	$141.58	7.116%	$151.6548	$151.65	$151.65	$151.70
Purchase #3	$198.77	7.171%	$213.0238	$213.02	$213.00	$213.00
Purchase #4	$206.40	7.540%	$221.9626	$221.96	$221.95	$222.00
Purchase #5	$144.40	12.852%	$162.9583	$162.96	$162.95	$163.00
Purchase #6	$72.52	9.461%	$79.3811	$79.38	$79.40	$79.40
Purchase #7	$82.47	8.200%	$89.2325	$89.23	$89.25	$89.20
7 purchase totals =	$915.51		$990.6277	$990.61	$990.60	$990.70