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	$214.50	3.714%	$222.4665	$222.47	$222.45	$222.50
Purchase #2	$170.97	7.833%	$184.3621	$184.36	$184.35	$184.40
Purchase #3	$162.95	7.280%	$174.8128	$174.81	$174.80	$174.80
Purchase #4	$60.35	9.262%	$65.9396	$65.94	$65.95	$65.90
Purchase #5	$81.52	5.652%	$86.1275	$86.13	$86.15	$86.10
Purchase #6	$53.70	7.862%	$57.9219	$57.92	$57.90	$57.90
Purchase #7	$190.83	10.630%	$211.1152	$211.12	$211.10	$211.10
7 purchase totals =	$934.82		$1,002.7456	$1,002.75	$1,002.70	$1,002.70