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	$153.98	8.372%	$166.8712	$166.87	$166.85	$166.90
Purchase #2	$184.73	7.496%	$198.5774	$198.58	$198.60	$198.60
Purchase #3	$108.81	11.731%	$121.5745	$121.57	$121.55	$121.60
Purchase #4	$103.85	7.234%	$111.3625	$111.36	$111.35	$111.40
Purchase #5	$24.53	11.828%	$27.4314	$27.43	$27.45	$27.40
Purchase #6	$171.95	4.873%	$180.3291	$180.33	$180.35	$180.30
Purchase #7	$141.90	11.166%	$157.7446	$157.74	$157.75	$157.70
7 purchase totals =	$889.75		$963.8907	$963.88	$963.90	$963.90