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	$90.91	13.222%	$102.9301	$102.93	$102.95	$102.90
Purchase #2	$57.76	4.473%	$60.3436	$60.34	$60.35	$60.30
Purchase #3	$135.84	13.285%	$153.8863	$153.89	$153.90	$153.90
Purchase #4	$85.66	7.275%	$91.8918	$91.89	$91.90	$91.90
Purchase #5	$214.46	12.606%	$241.4948	$241.49	$241.50	$241.50
Purchase #6	$206.65	5.593%	$218.2079	$218.21	$218.20	$218.20
Purchase #7	$215.44	11.779%	$240.8167	$240.82	$240.80	$240.80
7 purchase totals =	$1,006.72		$1,109.5712	$1,109.57	$1,109.60	$1,109.50