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	$86.32	6.506%	$91.936	$91.94	$91.95	$91.90
Purchase #2	$27.48	7.514%	$29.5448	$29.54	$29.55	$29.50
Purchase #3	$39.57	6.835%	$42.2746	$42.27	$42.25	$42.30
Purchase #4	$184.54	4.382%	$192.6265	$192.63	$192.65	$192.60
Purchase #5	$55.33	3.249%	$57.1277	$57.13	$57.15	$57.10
Purchase #6	$172.32	13.853%	$196.1915	$196.19	$196.20	$196.20
Purchase #7	$219.72	13.716%	$249.8568	$249.86	$249.85	$249.90
7 purchase totals =	$785.28		$859.5579	$859.56	$859.60	$859.50