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	$179.38	11.487%	$199.9854	$199.99	$200.00	$200.00
Purchase #2	$167.93	13.310%	$190.2815	$190.28	$190.30	$190.30
Purchase #3	$200.63	13.200%	$227.1132	$227.11	$227.10	$227.10
Purchase #4	$92.90	12.294%	$104.3211	$104.32	$104.30	$104.30
Purchase #5	$33.25	12.335%	$37.3514	$37.35	$37.35	$37.40
Purchase #6	$118.42	8.274%	$128.2181	$128.22	$128.20	$128.20
Purchase #7	$183.85	5.542%	$194.039	$194.04	$194.05	$194.00
7 purchase totals =	$976.36		$1,081.3097	$1,081.31	$1,081.30	$1,081.30