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	$57.32	8.508%	$62.1968	$62.20	$62.20	$62.20
Purchase #2	$58.89	4.178%	$61.3504	$61.35	$61.35	$61.40
Purchase #3	$226.61	9.377%	$247.8592	$247.86	$247.85	$247.90
Purchase #4	$212.79	8.814%	$231.5453	$231.55	$231.55	$231.50
Purchase #5	$223.31	10.521%	$246.8044	$246.80	$246.80	$246.80
Purchase #6	$116.41	6.110%	$123.5227	$123.52	$123.50	$123.50
Purchase #7	$104.57	11.718%	$116.8235	$116.82	$116.80	$116.80
7 purchase totals =	$999.90		$1,090.1023	$1,090.10	$1,090.05	$1,090.10