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	$66.86	8.393%	$72.4716	$72.47	$72.45	$72.50
Purchase #2	$62.54	13.393%	$70.916	$70.92	$70.90	$70.90
Purchase #3	$41.46	11.517%	$46.2349	$46.23	$46.25	$46.20
Purchase #4	$86.86	6.543%	$92.5432	$92.54	$92.55	$92.50
Purchase #5	$55.27	3.257%	$57.0701	$57.07	$57.05	$57.10
Purchase #6	$45.53	5.373%	$47.9763	$47.98	$48.00	$48.00
Purchase #7	$202.88	12.584%	$228.4104	$228.41	$228.40	$228.40
7 purchase totals =	$561.40		$615.6225	$615.62	$615.60	$615.60