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	$59.59	13.393%	$67.5709	$67.57	$67.55	$67.60
Purchase #2	$106.85	4.868%	$112.0515	$112.05	$112.05	$112.10
Purchase #3	$188.62	3.103%	$194.4729	$194.47	$194.45	$194.50
Purchase #4	$208.64	5.308%	$219.7146	$219.71	$219.70	$219.70
Purchase #5	$30.52	12.749%	$34.411	$34.41	$34.40	$34.40
Purchase #6	$178.29	11.636%	$199.0358	$199.04	$199.05	$199.00
Purchase #7	$232.32	13.856%	$264.5103	$264.51	$264.50	$264.50
7 purchase totals =	$1,004.83		$1,091.7670	$1,091.76	$1,091.70	$1,091.80