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	$99.56	11.593%	$111.102	$111.10	$111.10	$111.10
Purchase #2	$104.51	11.621%	$116.6551	$116.66	$116.65	$116.70
Purchase #3	$244.51	4.153%	$254.6645	$254.66	$254.65	$254.70
Purchase #4	$240.70	4.257%	$250.9466	$250.95	$250.95	$250.90
Purchase #5	$112.33	10.352%	$123.9584	$123.96	$123.95	$124.00
Purchase #6	$101.36	7.626%	$109.0897	$109.09	$109.10	$109.10
Purchase #7	$109.34	10.837%	$121.1892	$121.19	$121.20	$121.20
7 purchase totals =	$1,012.31		$1,087.6055	$1,087.61	$1,087.60	$1,087.70