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	$63.82	11.800%	$71.3508	$71.35	$71.35	$71.40
Purchase #2	$78.68	5.439%	$82.9594	$82.96	$82.95	$83.00
Purchase #3	$103.78	8.506%	$112.6075	$112.61	$112.60	$112.60
Purchase #4	$228.53	8.669%	$248.3413	$248.34	$248.35	$248.30
Purchase #5	$98.27	8.377%	$106.5021	$106.50	$106.50	$106.50
Purchase #6	$248.53	5.739%	$262.7931	$262.79	$262.80	$262.80
Purchase #7	$109.72	6.295%	$116.6269	$116.63	$116.65	$116.60
7 purchase totals =	$931.33		$1,001.1811	$1,001.18	$1,001.20	$1,001.20