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	$248.53	5.801%	$262.9472	$262.95	$262.95	$262.90
Purchase #2	$62.49	12.195%	$70.1107	$70.11	$70.10	$70.10
Purchase #3	$77.32	6.637%	$82.4517	$82.45	$82.45	$82.50
Purchase #4	$199.77	9.569%	$218.886	$218.89	$218.90	$218.90
Purchase #5	$148.68	9.506%	$162.8135	$162.81	$162.80	$162.80
Purchase #6	$55.87	7.287%	$59.9412	$59.94	$59.95	$59.90
Purchase #7	$40.87	8.316%	$44.2687	$44.27	$44.25	$44.30
7 purchase totals =	$833.53		$901.4190	$901.42	$901.40	$901.40