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	$93.79	10.473%	$103.6126	$103.61	$103.60	$103.60
Purchase #2	$52.37	12.731%	$59.0372	$59.04	$59.05	$59.00
Purchase #3	$111.61	8.299%	$120.8725	$120.87	$120.85	$120.90
Purchase #4	$145.70	6.787%	$155.5887	$155.59	$155.60	$155.60
Purchase #5	$183.95	8.239%	$199.1056	$199.11	$199.10	$199.10
Purchase #6	$240.48	9.797%	$264.0398	$264.04	$264.05	$264.00
Purchase #7	$134.95	7.402%	$144.939	$144.94	$144.95	$144.90
7 purchase totals =	$962.85		$1,047.1954	$1,047.20	$1,047.20	$1,047.10