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	$217.39	10.454%	$240.116	$240.12	$240.10	$240.10
Purchase #2	$200.32	12.683%	$225.7266	$225.73	$225.75	$225.70
Purchase #3	$152.32	6.649%	$162.4478	$162.45	$162.45	$162.40
Purchase #4	$109.55	6.541%	$116.7157	$116.72	$116.70	$116.70
Purchase #5	$109.46	4.498%	$114.3835	$114.38	$114.40	$114.40
Purchase #6	$20.72	5.765%	$21.9145	$21.91	$21.90	$21.90
Purchase #7	$163.32	7.730%	$175.9446	$175.94	$175.95	$175.90
7 purchase totals =	$973.08		$1,057.2487	$1,057.25	$1,057.25	$1,057.10