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	$112.45	12.320%	$126.3038	$126.30	$126.30	$126.30
Purchase #2	$63.98	11.352%	$71.243	$71.24	$71.25	$71.20
Purchase #3	$132.68	8.400%	$143.8251	$143.83	$143.85	$143.80
Purchase #4	$178.57	5.625%	$188.6146	$188.61	$188.60	$188.60
Purchase #5	$247.83	6.868%	$264.851	$264.85	$264.85	$264.90
Purchase #6	$157.77	6.369%	$167.8184	$167.82	$167.80	$167.80
Purchase #7	$77.33	11.465%	$86.1959	$86.20	$86.20	$86.20
7 purchase totals =	$970.61		$1,048.8518	$1,048.85	$1,048.85	$1,048.80