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	$54.93	4.703%	$57.5134	$57.51	$57.50	$57.50
Purchase #2	$171.76	10.818%	$190.341	$190.34	$190.35	$190.30
Purchase #3	$167.74	11.323%	$186.7332	$186.73	$186.75	$186.70
Purchase #4	$53.59	13.170%	$60.6478	$60.65	$60.65	$60.60
Purchase #5	$177.43	10.687%	$196.3919	$196.39	$196.40	$196.40
Purchase #6	$72.80	7.409%	$78.1938	$78.19	$78.20	$78.20
Purchase #7	$222.47	5.527%	$234.7659	$234.77	$234.75	$234.80
7 purchase totals =	$920.72		$1,004.5870	$1,004.58	$1,004.60	$1,004.50