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	$98.51	11.610%	$109.947	$109.95	$109.95	$109.90
Purchase #2	$234.96	12.546%	$264.4381	$264.44	$264.45	$264.40
Purchase #3	$53.57	3.116%	$55.2392	$55.24	$55.25	$55.20
Purchase #4	$132.30	6.508%	$140.9101	$140.91	$140.90	$140.90
Purchase #5	$26.59	11.254%	$29.5824	$29.58	$29.60	$29.60
Purchase #6	$237.48	11.299%	$264.3129	$264.31	$264.30	$264.30
Purchase #7	$245.86	6.752%	$262.4605	$262.46	$262.45	$262.50
7 purchase totals =	$1,029.27		$1,126.8902	$1,126.89	$1,126.90	$1,126.80