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	$126.30	5.626%	$133.4056	$133.41	$133.40	$133.40
Purchase #2	$203.36	3.418%	$210.3108	$210.31	$210.30	$210.30
Purchase #3	$95.36	10.713%	$105.5759	$105.58	$105.60	$105.60
Purchase #4	$101.82	3.843%	$105.7329	$105.73	$105.75	$105.70
Purchase #5	$100.32	5.624%	$105.962	$105.96	$105.95	$106.00
Purchase #6	$119.32	10.207%	$131.499	$131.50	$131.50	$131.50
Purchase #7	$167.41	5.790%	$177.103	$177.10	$177.10	$177.10
7 purchase totals =	$913.89		$969.5892	$969.59	$969.60	$969.60