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	$98.25	11.558%	$109.6057	$109.61	$109.60	$109.60
Purchase #2	$248.54	6.824%	$265.5004	$265.50	$265.50	$265.50
Purchase #3	$158.67	9.179%	$173.2343	$173.23	$173.25	$173.20
Purchase #4	$161.54	11.153%	$179.5566	$179.56	$179.55	$179.60
Purchase #5	$9.67	5.372%	$10.1895	$10.19	$10.20	$10.20
Purchase #6	$169.26	6.323%	$179.9623	$179.96	$179.95	$180.00
Purchase #7	$204.43	11.275%	$227.4795	$227.48	$227.50	$227.50
7 purchase totals =	$1,050.36		$1,145.5283	$1,145.53	$1,145.55	$1,145.60