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	$250.98	8.401%	$272.0648	$272.06	$272.05	$272.10
Purchase #2	$179.58	11.840%	$200.8423	$200.84	$200.85	$200.80
Purchase #3	$140.51	7.811%	$151.4852	$151.49	$151.50	$151.50
Purchase #4	$151.45	12.130%	$169.8209	$169.82	$169.80	$169.80
Purchase #5	$47.97	9.250%	$52.4072	$52.41	$52.40	$52.40
Purchase #6	$187.82	3.578%	$194.5402	$194.54	$194.55	$194.50
Purchase #7	$101.81	10.614%	$112.6161	$112.62	$112.60	$112.60
7 purchase totals =	$1,060.12		$1,153.7767	$1,153.78	$1,153.75	$1,153.70