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	$45.75	4.628%	$47.8673	$47.87	$47.85	$47.90
Purchase #2	$14.37	3.654%	$14.8951	$14.90	$14.90	$14.90
Purchase #3	$136.42	10.565%	$150.8328	$150.83	$150.85	$150.80
Purchase #4	$57.50	8.760%	$62.537	$62.54	$62.55	$62.50
Purchase #5	$62.26	6.332%	$66.2023	$66.20	$66.20	$66.20
Purchase #6	$17.92	13.850%	$20.4019	$20.40	$20.40	$20.40
Purchase #7	$218.67	9.205%	$238.7986	$238.80	$238.80	$238.80
7 purchase totals =	$552.89		$601.5350	$601.54	$601.55	$601.50