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	$22.76	13.754%	$25.8904	$25.89	$25.90	$25.90
Purchase #2	$78.83	3.117%	$81.2871	$81.29	$81.30	$81.30
Purchase #3	$61.38	12.127%	$68.8236	$68.82	$68.80	$68.80
Purchase #4	$90.90	4.782%	$95.2468	$95.25	$95.25	$95.20
Purchase #5	$195.31	12.390%	$219.5089	$219.51	$219.50	$219.50
Purchase #6	$171.33	10.166%	$188.7474	$188.75	$188.75	$188.70
Purchase #7	$141.84	7.756%	$152.8411	$152.84	$152.85	$152.80
7 purchase totals =	$762.35		$832.3453	$832.35	$832.35	$832.20