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	$88.90	11.659%	$99.2649	$99.26	$99.25	$99.30
Purchase #2	$34.78	5.797%	$36.7962	$36.80	$36.80	$36.80
Purchase #3	$160.88	13.673%	$182.8771	$182.88	$182.90	$182.90
Purchase #4	$155.88	10.393%	$172.0806	$172.08	$172.10	$172.10
Purchase #5	$237.25	5.168%	$249.5111	$249.51	$249.50	$249.50
Purchase #6	$152.98	5.360%	$161.1797	$161.18	$161.20	$161.20
Purchase #7	$162.26	6.343%	$172.5522	$172.55	$172.55	$172.60
7 purchase totals =	$992.93		$1,074.2618	$1,074.26	$1,074.30	$1,074.40