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	$166.43	8.483%	$180.5483	$180.55	$180.55	$180.50
Purchase #2	$186.89	5.688%	$197.5203	$197.52	$197.50	$197.50
Purchase #3	$248.99	13.467%	$282.5215	$282.52	$282.50	$282.50
Purchase #4	$46.31	12.868%	$52.2692	$52.27	$52.25	$52.30
Purchase #5	$150.66	11.716%	$168.3113	$168.31	$168.30	$168.30
Purchase #6	$163.67	7.112%	$175.3102	$175.31	$175.30	$175.30
Purchase #7	$9.44	9.342%	$10.3219	$10.32	$10.30	$10.30
7 purchase totals =	$972.39		$1,066.8027	$1,066.80	$1,066.70	$1,066.70