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	$76.43	8.426%	$82.87	$82.87	$82.85	$82.90
Purchase #2	$41.54	3.768%	$43.1052	$43.11	$43.10	$43.10
Purchase #3	$25.28	13.211%	$28.6197	$28.62	$28.60	$28.60
Purchase #4	$212.69	10.412%	$234.8353	$234.84	$234.85	$234.80
Purchase #5	$46.58	9.114%	$50.8253	$50.83	$50.85	$50.80
Purchase #6	$200.90	4.750%	$210.4428	$210.44	$210.45	$210.40
Purchase #7	$30.38	3.690%	$31.501	$31.50	$31.50	$31.50
7 purchase totals =	$633.80		$682.1993	$682.21	$682.20	$682.10