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	$13.40	8.315%	$14.5142	$14.51	$14.50	$14.50
Purchase #2	$120.29	10.866%	$133.3607	$133.36	$133.35	$133.40
Purchase #3	$205.87	3.410%	$212.8902	$212.89	$212.90	$212.90
Purchase #4	$31.86	4.285%	$33.2252	$33.23	$33.25	$33.20
Purchase #5	$144.36	3.820%	$149.8746	$149.87	$149.85	$149.90
Purchase #6	$211.61	13.605%	$240.3995	$240.40	$240.40	$240.40
Purchase #7	$201.44	10.640%	$222.8732	$222.87	$222.85	$222.90
7 purchase totals =	$928.83		$1,007.1376	$1,007.13	$1,007.10	$1,007.20