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	$160.65	3.220%	$165.8229	$165.82	$165.80	$165.80
Purchase #2	$90.25	4.715%	$94.5053	$94.51	$94.50	$94.50
Purchase #3	$97.30	6.312%	$103.4416	$103.44	$103.45	$103.40
Purchase #4	$175.75	5.213%	$184.9118	$184.91	$184.90	$184.90
Purchase #5	$131.46	12.147%	$147.4284	$147.43	$147.45	$147.40
Purchase #6	$24.57	3.725%	$25.4852	$25.49	$25.50	$25.50
Purchase #7	$125.71	4.227%	$131.0238	$131.02	$131.00	$131.00
7 purchase totals =	$805.69		$852.6190	$852.62	$852.60	$852.50