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	$163.26	13.470%	$185.2511	$185.25	$185.25	$185.30
Purchase #2	$151.44	11.127%	$168.2907	$168.29	$168.30	$168.30
Purchase #3	$49.31	6.331%	$52.4318	$52.43	$52.45	$52.40
Purchase #4	$118.70	12.809%	$133.9043	$133.90	$133.90	$133.90
Purchase #5	$183.96	13.268%	$208.3678	$208.37	$208.35	$208.40
Purchase #6	$74.79	11.819%	$83.6294	$83.63	$83.65	$83.60
Purchase #7	$97.90	13.420%	$111.0382	$111.04	$111.05	$111.00
7 purchase totals =	$839.36		$942.9133	$942.91	$942.95	$942.90