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	$88.49	4.229%	$92.2322	$92.23	$92.25	$92.20
Purchase #2	$177.89	9.366%	$194.5512	$194.55	$194.55	$194.60
Purchase #3	$212.69	11.334%	$236.7963	$236.80	$236.80	$236.80
Purchase #4	$49.61	7.184%	$53.174	$53.17	$53.15	$53.20
Purchase #5	$94.47	6.844%	$100.9355	$100.94	$100.95	$100.90
Purchase #6	$11.87	11.566%	$13.2429	$13.24	$13.25	$13.20
Purchase #7	$181.76	13.276%	$205.8905	$205.89	$205.90	$205.90
7 purchase totals =	$816.78		$896.8226	$896.82	$896.85	$896.80