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	$88.95	10.730%	$98.4943	$98.49	$98.50	$98.50
Purchase #2	$115.99	6.273%	$123.2661	$123.27	$123.25	$123.30
Purchase #3	$164.38	4.732%	$172.1585	$172.16	$172.15	$172.20
Purchase #4	$101.79	4.591%	$106.4632	$106.46	$106.45	$106.50
Purchase #5	$41.53	4.845%	$43.5421	$43.54	$43.55	$43.50
Purchase #6	$131.75	9.504%	$144.2715	$144.27	$144.25	$144.30
Purchase #7	$186.62	10.621%	$206.4409	$206.44	$206.45	$206.40
7 purchase totals =	$831.01		$894.6366	$894.63	$894.60	$894.70