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	$101.42	3.857%	$105.3318	$105.33	$105.35	$105.30
Purchase #2	$55.71	8.200%	$60.2782	$60.28	$60.30	$60.30
Purchase #3	$243.59	11.519%	$271.6491	$271.65	$271.65	$271.60
Purchase #4	$193.26	11.352%	$215.1989	$215.20	$215.20	$215.20
Purchase #5	$125.41	13.749%	$142.6526	$142.65	$142.65	$142.70
Purchase #6	$90.69	4.176%	$94.4772	$94.48	$94.50	$94.50
Purchase #7	$38.95	12.712%	$43.9013	$43.90	$43.90	$43.90
7 purchase totals =	$849.03		$933.4891	$933.49	$933.55	$933.50