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	$98.56	5.847%	$104.3228	$104.32	$104.30	$104.30
Purchase #2	$45.42	4.219%	$47.3363	$47.34	$47.35	$47.30
Purchase #3	$41.47	12.812%	$46.7831	$46.78	$46.80	$46.80
Purchase #4	$104.83	6.572%	$111.7194	$111.72	$111.70	$111.70
Purchase #5	$30.78	10.647%	$34.0571	$34.06	$34.05	$34.10
Purchase #6	$131.90	11.364%	$146.8891	$146.89	$146.90	$146.90
Purchase #7	$84.32	12.235%	$94.6366	$94.64	$94.65	$94.60
7 purchase totals =	$537.28		$585.7444	$585.75	$585.75	$585.70