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	$126.70	10.308%	$139.7602	$139.76	$139.75	$139.80
Purchase #2	$185.60	4.769%	$194.4513	$194.45	$194.45	$194.50
Purchase #3	$33.85	12.526%	$38.0901	$38.09	$38.10	$38.10
Purchase #4	$173.97	7.167%	$186.4384	$186.44	$186.45	$186.40
Purchase #5	$194.69	10.797%	$215.7107	$215.71	$215.70	$215.70
Purchase #6	$223.92	13.587%	$254.344	$254.34	$254.35	$254.30
Purchase #7	$87.92	13.653%	$99.9237	$99.92	$99.90	$99.90
7 purchase totals =	$1,026.65		$1,128.7184	$1,128.71	$1,128.70	$1,128.70