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	$87.82	13.210%	$99.421	$99.42	$99.40	$99.40
Purchase #2	$85.87	10.639%	$95.0057	$95.01	$95.00	$95.00
Purchase #3	$175.97	3.348%	$181.8615	$181.86	$181.85	$181.90
Purchase #4	$46.74	13.541%	$53.0691	$53.07	$53.05	$53.10
Purchase #5	$222.64	6.260%	$236.5773	$236.58	$236.60	$236.60
Purchase #6	$208.55	8.121%	$225.4863	$225.49	$225.50	$225.50
Purchase #7	$197.46	12.471%	$222.0852	$222.09	$222.10	$222.10
7 purchase totals =	$1,025.05		$1,113.5061	$1,113.52	$1,113.50	$1,113.60