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	$188.34	12.811%	$212.4682	$212.47	$212.45	$212.50
Purchase #2	$56.81	5.311%	$59.8272	$59.83	$59.85	$59.80
Purchase #3	$192.65	4.189%	$200.7201	$200.72	$200.70	$200.70
Purchase #4	$110.66	4.464%	$115.5999	$115.60	$115.60	$115.60
Purchase #5	$169.89	3.753%	$176.266	$176.27	$176.25	$176.30
Purchase #6	$49.90	8.758%	$54.2702	$54.27	$54.25	$54.30
Purchase #7	$245.60	3.658%	$254.584	$254.58	$254.60	$254.60
7 purchase totals =	$1,013.85		$1,073.7356	$1,073.74	$1,073.70	$1,073.80