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	$41.30	4.216%	$43.0412	$43.04	$43.05	$43.00
Purchase #2	$171.64	6.766%	$183.2532	$183.25	$183.25	$183.30
Purchase #3	$206.29	5.622%	$217.8876	$217.89	$217.90	$217.90
Purchase #4	$136.69	4.277%	$142.5362	$142.54	$142.55	$142.50
Purchase #5	$131.97	7.415%	$141.7556	$141.76	$141.75	$141.80
Purchase #6	$167.90	3.747%	$174.1912	$174.19	$174.20	$174.20
Purchase #7	$40.94	11.739%	$45.7459	$45.75	$45.75	$45.70
7 purchase totals =	$896.73		$948.4109	$948.42	$948.45	$948.40