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	$8.26	8.223%	$8.9392	$8.94	$8.95	$8.90
Purchase #2	$12.42	11.275%	$13.8204	$13.82	$13.80	$13.80
Purchase #3	$102.65	6.237%	$109.0523	$109.05	$109.05	$109.10
Purchase #4	$165.92	10.847%	$183.9173	$183.92	$183.90	$183.90
Purchase #5	$91.85	9.821%	$100.8706	$100.87	$100.85	$100.90
Purchase #6	$166.35	10.795%	$184.3075	$184.31	$184.30	$184.30
Purchase #7	$80.89	9.402%	$88.4953	$88.50	$88.50	$88.50
7 purchase totals =	$628.34		$689.4026	$689.41	$689.35	$689.40