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	$101.44	10.110%	$111.6956	$111.70	$111.70	$111.70
Purchase #2	$124.34	6.611%	$132.5601	$132.56	$132.55	$132.60
Purchase #3	$174.27	6.567%	$185.7143	$185.71	$185.70	$185.70
Purchase #4	$104.62	8.843%	$113.8715	$113.87	$113.85	$113.90
Purchase #5	$101.99	5.452%	$107.5505	$107.55	$107.55	$107.60
Purchase #6	$225.31	13.438%	$255.5872	$255.59	$255.60	$255.60
Purchase #7	$165.38	10.806%	$183.251	$183.25	$183.25	$183.30
7 purchase totals =	$997.35		$1,090.2302	$1,090.23	$1,090.20	$1,090.40