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	$183.82	12.851%	$207.4427	$207.44	$207.45	$207.40
Purchase #2	$66.65	9.580%	$73.0351	$73.04	$73.05	$73.00
Purchase #3	$150.99	12.138%	$169.3172	$169.32	$169.30	$169.30
Purchase #4	$110.54	7.112%	$118.4016	$118.40	$118.40	$118.40
Purchase #5	$179.83	13.700%	$204.4667	$204.47	$204.45	$204.50
Purchase #6	$205.39	8.320%	$222.4784	$222.48	$222.50	$222.50
Purchase #7	$19.43	7.317%	$20.8517	$20.85	$20.85	$20.90
7 purchase totals =	$916.65		$1,015.9934	$1,016.00	$1,016.00	$1,016.00