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	$248.83	4.670%	$260.4504	$260.45	$260.45	$260.50
Purchase #2	$233.86	7.291%	$250.9107	$250.91	$250.90	$250.90
Purchase #3	$21.86	10.464%	$24.1474	$24.15	$24.15	$24.10
Purchase #4	$232.71	10.711%	$257.6356	$257.64	$257.65	$257.60
Purchase #5	$165.76	9.718%	$181.8686	$181.87	$181.85	$181.90
Purchase #6	$80.75	3.834%	$83.846	$83.85	$83.85	$83.80
Purchase #7	$28.50	9.671%	$31.2562	$31.26	$31.25	$31.30
7 purchase totals =	$1,012.27		$1,090.1149	$1,090.13	$1,090.10	$1,090.10