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	$123.92	7.789%	$133.5721	$133.57	$133.55	$133.60
Purchase #2	$112.47	13.661%	$127.8345	$127.83	$127.85	$127.80
Purchase #3	$116.43	6.280%	$123.7418	$123.74	$123.75	$123.70
Purchase #4	$124.51	7.532%	$133.8881	$133.89	$133.90	$133.90
Purchase #5	$49.69	4.834%	$52.092	$52.09	$52.10	$52.10
Purchase #6	$245.41	12.626%	$276.3955	$276.40	$276.40	$276.40
Purchase #7	$73.32	12.671%	$82.6104	$82.61	$82.60	$82.60
7 purchase totals =	$845.75		$930.1344	$930.13	$930.15	$930.10