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	$218.42	10.490%	$241.3323	$241.33	$241.35	$241.30
Purchase #2	$168.76	6.867%	$180.3487	$180.35	$180.35	$180.30
Purchase #3	$236.70	5.706%	$250.2061	$250.21	$250.20	$250.20
Purchase #4	$15.61	11.342%	$17.3805	$17.38	$17.40	$17.40
Purchase #5	$80.82	10.531%	$89.3312	$89.33	$89.35	$89.30
Purchase #6	$141.79	10.257%	$156.3334	$156.33	$156.35	$156.30
Purchase #7	$95.31	4.110%	$99.2272	$99.23	$99.25	$99.20
7 purchase totals =	$957.41		$1,034.1594	$1,034.16	$1,034.25	$1,034.00