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	$31.54	12.554%	$35.4995	$35.50	$35.50	$35.50
Purchase #2	$11.69	10.820%	$12.9549	$12.95	$12.95	$13.00
Purchase #3	$86.40	3.811%	$89.6927	$89.69	$89.70	$89.70
Purchase #4	$93.31	6.146%	$99.0448	$99.04	$99.05	$99.00
Purchase #5	$85.91	5.211%	$90.3868	$90.39	$90.40	$90.40
Purchase #6	$194.71	7.218%	$208.7642	$208.76	$208.75	$208.80
Purchase #7	$248.43	11.496%	$276.9895	$276.99	$277.00	$277.00
7 purchase totals =	$751.99		$813.3324	$813.32	$813.35	$813.40