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	$88.32	4.747%	$92.5126	$92.51	$92.50	$92.50
Purchase #2	$111.69	12.699%	$125.8735	$125.87	$125.85	$125.90
Purchase #3	$199.57	13.229%	$225.9711	$225.97	$225.95	$226.00
Purchase #4	$237.56	13.161%	$268.8253	$268.83	$268.85	$268.80
Purchase #5	$31.94	3.108%	$32.9327	$32.93	$32.95	$32.90
Purchase #6	$119.37	7.746%	$128.6164	$128.62	$128.60	$128.60
Purchase #7	$179.57	3.654%	$186.1315	$186.13	$186.15	$186.10
7 purchase totals =	$968.02		$1,060.8631	$1,060.86	$1,060.85	$1,060.80