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	$191.78	10.702%	$212.3043	$212.30	$212.30	$212.30
Purchase #2	$155.66	11.651%	$173.7959	$173.80	$173.80	$173.80
Purchase #3	$197.55	3.821%	$205.0984	$205.10	$205.10	$205.10
Purchase #4	$64.25	10.573%	$71.0432	$71.04	$71.05	$71.00
Purchase #5	$123.54	3.196%	$127.4883	$127.49	$127.50	$127.50
Purchase #6	$115.43	8.544%	$125.2923	$125.29	$125.30	$125.30
Purchase #7	$87.30	5.240%	$91.8745	$91.87	$91.85	$91.90
7 purchase totals =	$935.51		$1,006.8969	$1,006.89	$1,006.90	$1,006.90