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	$32.64	7.415%	$35.0603	$35.06	$35.05	$35.10
Purchase #2	$18.40	13.726%	$20.9256	$20.93	$20.95	$20.90
Purchase #3	$45.94	11.624%	$51.2801	$51.28	$51.30	$51.30
Purchase #4	$45.54	12.640%	$51.2963	$51.30	$51.30	$51.30
Purchase #5	$96.87	12.102%	$108.5932	$108.59	$108.60	$108.60
Purchase #6	$38.73	11.269%	$43.0945	$43.09	$43.10	$43.10
Purchase #7	$52.75	7.862%	$56.8972	$56.90	$56.90	$56.90
7 purchase totals =	$330.87		$367.1472	$367.15	$367.20	$367.20