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	$94.43	11.383%	$105.179	$105.18	$105.20	$105.20
Purchase #2	$193.97	9.249%	$211.9103	$211.91	$211.90	$211.90
Purchase #3	$240.91	6.827%	$257.3569	$257.36	$257.35	$257.40
Purchase #4	$45.50	7.426%	$48.8788	$48.88	$48.90	$48.90
Purchase #5	$198.38	12.646%	$223.4671	$223.47	$223.45	$223.50
Purchase #6	$109.68	10.168%	$120.8323	$120.83	$120.85	$120.80
Purchase #7	$122.44	8.270%	$132.5658	$132.57	$132.55	$132.60
7 purchase totals =	$1,005.31		$1,100.1902	$1,100.20	$1,100.20	$1,100.30