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	$178.76	7.501%	$192.1688	$192.17	$192.15	$192.20
Purchase #2	$148.83	9.440%	$162.8796	$162.88	$162.90	$162.90
Purchase #3	$198.97	8.324%	$215.5323	$215.53	$215.55	$215.50
Purchase #4	$158.85	7.343%	$170.5144	$170.51	$170.50	$170.50
Purchase #5	$141.90	7.696%	$152.8206	$152.82	$152.80	$152.80
Purchase #6	$131.60	3.585%	$136.3179	$136.32	$136.30	$136.30
Purchase #7	$100.38	3.301%	$103.6935	$103.69	$103.70	$103.70
7 purchase totals =	$1,059.29		$1,133.9271	$1,133.92	$1,133.90	$1,133.90