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	$66.47	10.445%	$73.4128	$73.41	$73.40	$73.40
Purchase #2	$59.34	7.837%	$63.9905	$63.99	$64.00	$64.00
Purchase #3	$196.55	7.391%	$211.077	$211.08	$211.10	$211.10
Purchase #4	$209.42	4.312%	$218.4502	$218.45	$218.45	$218.50
Purchase #5	$83.97	12.705%	$94.6384	$94.64	$94.65	$94.60
Purchase #6	$41.66	4.272%	$43.4397	$43.44	$43.45	$43.40
Purchase #7	$56.51	5.341%	$59.5282	$59.53	$59.55	$59.50
7 purchase totals =	$713.92		$764.5368	$764.54	$764.60	$764.50