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	$86.87	10.387%	$95.8932	$95.89	$95.90	$95.90
Purchase #2	$218.95	6.568%	$233.3306	$233.33	$233.35	$233.30
Purchase #3	$148.83	9.145%	$162.4405	$162.44	$162.45	$162.40
Purchase #4	$194.76	10.862%	$215.9148	$215.91	$215.90	$215.90
Purchase #5	$115.43	3.132%	$119.0453	$119.05	$119.05	$119.00
Purchase #6	$197.29	6.429%	$209.9738	$209.97	$209.95	$210.00
Purchase #7	$41.54	5.513%	$43.8301	$43.83	$43.85	$43.80
7 purchase totals =	$1,003.67		$1,080.4283	$1,080.42	$1,080.45	$1,080.30