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	$141.43	8.815%	$153.8971	$153.90	$153.90	$153.90
Purchase #2	$9.84	9.784%	$10.8027	$10.80	$10.80	$10.80
Purchase #3	$65.53	8.578%	$71.1512	$71.15	$71.15	$71.20
Purchase #4	$145.43	13.105%	$164.4886	$164.49	$164.50	$164.50
Purchase #5	$237.80	10.822%	$263.5347	$263.53	$263.55	$263.50
Purchase #6	$95.69	10.324%	$105.569	$105.57	$105.55	$105.60
Purchase #7	$82.94	6.234%	$88.1105	$88.11	$88.10	$88.10
7 purchase totals =	$778.66		$857.5538	$857.55	$857.55	$857.60