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	$63.57	3.454%	$65.7657	$65.77	$65.75	$65.80
Purchase #2	$159.91	4.163%	$166.5671	$166.57	$166.55	$166.60
Purchase #3	$246.60	11.360%	$274.6138	$274.61	$274.60	$274.60
Purchase #4	$118.83	7.786%	$128.0821	$128.08	$128.10	$128.10
Purchase #5	$169.81	13.595%	$192.8957	$192.90	$192.90	$192.90
Purchase #6	$244.79	11.447%	$272.8111	$272.81	$272.80	$272.80
Purchase #7	$76.74	10.862%	$85.0755	$85.08	$85.10	$85.10
7 purchase totals =	$1,080.25		$1,185.8110	$1,185.82	$1,185.80	$1,185.90