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	$108.30	9.712%	$118.8181	$118.82	$118.80	$118.80
Purchase #2	$212.28	11.669%	$237.051	$237.05	$237.05	$237.10
Purchase #3	$10.33	6.162%	$10.9665	$10.97	$10.95	$11.00
Purchase #4	$228.47	6.172%	$242.5712	$242.57	$242.55	$242.60
Purchase #5	$7.96	7.708%	$8.5736	$8.57	$8.55	$8.60
Purchase #6	$246.87	11.127%	$274.3392	$274.34	$274.35	$274.30
Purchase #7	$212.38	3.353%	$219.5011	$219.50	$219.50	$219.50
7 purchase totals =	$1,026.59		$1,111.8207	$1,111.82	$1,111.75	$1,111.90