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	$223.69	8.604%	$242.9363	$242.94	$242.95	$242.90
Purchase #2	$28.49	4.871%	$29.8777	$29.88	$29.90	$29.90
Purchase #3	$201.25	5.259%	$211.8337	$211.83	$211.85	$211.80
Purchase #4	$96.46	12.803%	$108.8098	$108.81	$108.80	$108.80
Purchase #5	$175.60	11.848%	$196.4051	$196.41	$196.40	$196.40
Purchase #6	$52.79	7.235%	$56.6094	$56.61	$56.60	$56.60
Purchase #7	$39.67	10.431%	$43.808	$43.81	$43.80	$43.80
7 purchase totals =	$817.95		$890.2800	$890.29	$890.30	$890.20