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	$100.34	11.377%	$111.7557	$111.76	$111.75	$111.80
Purchase #2	$232.57	7.536%	$250.0965	$250.10	$250.10	$250.10
Purchase #3	$213.25	7.220%	$228.6467	$228.65	$228.65	$228.60
Purchase #4	$235.80	12.762%	$265.8928	$265.89	$265.90	$265.90
Purchase #5	$51.92	3.219%	$53.5913	$53.59	$53.60	$53.60
Purchase #6	$34.97	11.858%	$39.1167	$39.12	$39.10	$39.10
Purchase #7	$187.60	3.528%	$194.2185	$194.22	$194.20	$194.20
7 purchase totals =	$1,056.45		$1,143.3182	$1,143.33	$1,143.30	$1,143.30