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	$230.59	5.619%	$243.5469	$243.55	$243.55	$243.50
Purchase #2	$94.34	8.371%	$102.2372	$102.24	$102.25	$102.20
Purchase #3	$95.57	10.568%	$105.6698	$105.67	$105.65	$105.70
Purchase #4	$175.32	9.623%	$192.191	$192.19	$192.20	$192.20
Purchase #5	$56.88	5.214%	$59.8457	$59.85	$59.85	$59.80
Purchase #6	$246.81	13.322%	$279.69	$279.69	$279.70	$279.70
Purchase #7	$152.25	11.514%	$169.7801	$169.78	$169.80	$169.80
7 purchase totals =	$1,051.76		$1,152.9607	$1,152.97	$1,153.00	$1,152.90