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	$185.55	13.140%	$209.9313	$209.93	$209.95	$209.90
Purchase #2	$60.71	10.582%	$67.1343	$67.13	$67.15	$67.10
Purchase #3	$126.98	12.169%	$142.4322	$142.43	$142.45	$142.40
Purchase #4	$139.52	5.605%	$147.3401	$147.34	$147.35	$147.30
Purchase #5	$213.83	13.347%	$242.3699	$242.37	$242.35	$242.40
Purchase #6	$181.51	9.394%	$198.561	$198.56	$198.55	$198.60
Purchase #7	$172.28	9.738%	$189.0566	$189.06	$189.05	$189.10
7 purchase totals =	$1,080.38		$1,196.8254	$1,196.82	$1,196.85	$1,196.80