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	$191.70	9.779%	$210.4463	$210.45	$210.45	$210.40
Purchase #2	$32.59	11.175%	$36.2319	$36.23	$36.25	$36.20
Purchase #3	$123.31	7.164%	$132.1439	$132.14	$132.15	$132.10
Purchase #4	$211.69	13.635%	$240.5539	$240.55	$240.55	$240.60
Purchase #5	$127.78	5.167%	$134.3824	$134.38	$134.40	$134.40
Purchase #6	$205.42	3.498%	$212.6056	$212.61	$212.60	$212.60
Purchase #7	$117.31	6.509%	$124.9457	$124.95	$124.95	$124.90
7 purchase totals =	$1,009.80		$1,091.3097	$1,091.31	$1,091.35	$1,091.20