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	$237.76	10.790%	$263.4143	$263.41	$263.40	$263.40
Purchase #2	$42.26	5.234%	$44.4719	$44.47	$44.45	$44.50
Purchase #3	$114.57	11.126%	$127.3171	$127.32	$127.30	$127.30
Purchase #4	$39.86	9.218%	$43.5343	$43.53	$43.55	$43.50
Purchase #5	$55.56	13.304%	$62.9517	$62.95	$62.95	$63.00
Purchase #6	$20.54	4.167%	$21.3959	$21.40	$21.40	$21.40
Purchase #7	$57.55	13.368%	$65.2433	$65.24	$65.25	$65.20
7 purchase totals =	$568.10		$628.3285	$628.32	$628.30	$628.30