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	$247.31	7.632%	$266.1847	$266.18	$266.20	$266.20
Purchase #2	$209.78	3.834%	$217.823	$217.82	$217.80	$217.80
Purchase #3	$145.34	4.832%	$152.3628	$152.36	$152.35	$152.40
Purchase #4	$68.52	7.839%	$73.8913	$73.89	$73.90	$73.90
Purchase #5	$87.80	8.648%	$95.3929	$95.39	$95.40	$95.40
Purchase #6	$85.99	7.596%	$92.5218	$92.52	$92.50	$92.50
Purchase #7	$238.69	5.532%	$251.8943	$251.89	$251.90	$251.90
7 purchase totals =	$1,083.43		$1,150.0708	$1,150.05	$1,150.05	$1,150.10