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	$107.84	3.451%	$111.5616	$111.56	$111.55	$111.60
Purchase #2	$95.43	3.859%	$99.1126	$99.11	$99.10	$99.10
Purchase #3	$38.90	10.112%	$42.8336	$42.83	$42.85	$42.80
Purchase #4	$188.52	9.689%	$206.7857	$206.79	$206.80	$206.80
Purchase #5	$250.64	9.156%	$273.5886	$273.59	$273.60	$273.60
Purchase #6	$199.84	10.867%	$221.5566	$221.56	$221.55	$221.60
Purchase #7	$240.62	8.867%	$261.9558	$261.96	$261.95	$262.00
7 purchase totals =	$1,121.79		$1,217.3945	$1,217.40	$1,217.40	$1,217.50