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	$103.38	7.775%	$111.4178	$111.42	$111.40	$111.40
Purchase #2	$149.89	9.350%	$163.9047	$163.90	$163.90	$163.90
Purchase #3	$120.96	5.116%	$127.1483	$127.15	$127.15	$127.10
Purchase #4	$114.83	13.496%	$130.3275	$130.33	$130.35	$130.30
Purchase #5	$83.40	5.835%	$88.2664	$88.27	$88.25	$88.30
Purchase #6	$237.54	3.176%	$245.0843	$245.08	$245.10	$245.10
Purchase #7	$14.56	6.554%	$15.5143	$15.51	$15.50	$15.50
7 purchase totals =	$824.56		$881.6633	$881.66	$881.65	$881.60