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	$83.37	13.796%	$94.8717	$94.87	$94.85	$94.90
Purchase #2	$12.31	6.136%	$13.0653	$13.07	$13.05	$13.10
Purchase #3	$244.61	13.466%	$277.5492	$277.55	$277.55	$277.50
Purchase #4	$136.78	10.143%	$150.6536	$150.65	$150.65	$150.70
Purchase #5	$130.90	9.193%	$142.9336	$142.93	$142.95	$142.90
Purchase #6	$73.70	5.647%	$77.8618	$77.86	$77.85	$77.90
Purchase #7	$85.51	5.149%	$89.9129	$89.91	$89.90	$89.90
7 purchase totals =	$767.18		$846.8481	$846.84	$846.80	$846.90