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	$230.67	8.426%	$250.1063	$250.11	$250.10	$250.10
Purchase #2	$9.69	4.784%	$10.1536	$10.15	$10.15	$10.20
Purchase #3	$111.98	12.352%	$125.8118	$125.81	$125.80	$125.80
Purchase #4	$83.95	4.682%	$87.8805	$87.88	$87.90	$87.90
Purchase #5	$104.30	8.777%	$113.4544	$113.45	$113.45	$113.50
Purchase #6	$109.25	3.109%	$112.6466	$112.65	$112.65	$112.60
Purchase #7	$158.47	3.558%	$164.1084	$164.11	$164.10	$164.10
7 purchase totals =	$808.31		$864.1616	$864.16	$864.15	$864.20