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	$99.35	11.749%	$111.0226	$111.02	$111.00	$111.00
Purchase #2	$45.40	7.615%	$48.8572	$48.86	$48.85	$48.90
Purchase #3	$21.26	6.440%	$22.6291	$22.63	$22.65	$22.60
Purchase #4	$35.76	8.119%	$38.6634	$38.66	$38.65	$38.70
Purchase #5	$195.62	9.853%	$214.8944	$214.89	$214.90	$214.90
Purchase #6	$131.99	13.672%	$150.0357	$150.04	$150.05	$150.00
Purchase #7	$194.40	12.857%	$219.394	$219.39	$219.40	$219.40
7 purchase totals =	$723.78		$805.4964	$805.49	$805.50	$805.50