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	$168.88	7.533%	$181.6017	$181.60	$181.60	$181.60
Purchase #2	$6.86	10.296%	$7.5663	$7.57	$7.55	$7.60
Purchase #3	$217.30	5.614%	$229.4992	$229.50	$229.50	$229.50
Purchase #4	$237.88	10.471%	$262.7884	$262.79	$262.80	$262.80
Purchase #5	$91.38	13.281%	$103.5162	$103.52	$103.50	$103.50
Purchase #6	$34.46	8.120%	$37.2582	$37.26	$37.25	$37.30
Purchase #7	$204.99	6.393%	$218.095	$218.10	$218.10	$218.10
7 purchase totals =	$961.75		$1,040.3250	$1,040.34	$1,040.30	$1,040.40