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	$218.74	9.149%	$238.7525	$238.75	$238.75	$238.80
Purchase #2	$65.62	10.171%	$72.2942	$72.29	$72.30	$72.30
Purchase #3	$244.46	6.264%	$259.773	$259.77	$259.75	$259.80
Purchase #4	$90.99	4.277%	$94.8816	$94.88	$94.90	$94.90
Purchase #5	$156.37	13.781%	$177.9193	$177.92	$177.90	$177.90
Purchase #6	$145.75	13.733%	$165.7658	$165.77	$165.75	$165.80
Purchase #7	$73.57	12.853%	$83.026	$83.03	$83.05	$83.00
7 purchase totals =	$995.50		$1,092.4124	$1,092.41	$1,092.40	$1,092.50