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	$172.32	10.362%	$190.1758	$190.18	$190.20	$190.20
Purchase #2	$23.81	5.688%	$25.1643	$25.16	$25.15	$25.20
Purchase #3	$146.91	10.690%	$162.6147	$162.61	$162.60	$162.60
Purchase #4	$16.77	10.645%	$18.5552	$18.56	$18.55	$18.60
Purchase #5	$205.36	4.503%	$214.6074	$214.61	$214.60	$214.60
Purchase #6	$210.83	10.599%	$233.1759	$233.18	$233.20	$233.20
Purchase #7	$105.47	3.714%	$109.3872	$109.39	$109.40	$109.40
7 purchase totals =	$881.47		$953.6805	$953.69	$953.70	$953.80