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	$208.83	8.448%	$226.472	$226.47	$226.45	$226.50
Purchase #2	$19.29	5.843%	$20.4171	$20.42	$20.40	$20.40
Purchase #3	$55.30	7.747%	$59.5841	$59.58	$59.60	$59.60
Purchase #4	$7.38	13.436%	$8.3716	$8.37	$8.35	$8.40
Purchase #5	$20.36	6.496%	$21.6826	$21.68	$21.70	$21.70
Purchase #6	$99.94	13.623%	$113.5548	$113.55	$113.55	$113.60
Purchase #7	$142.96	6.376%	$152.0751	$152.08	$152.10	$152.10
7 purchase totals =	$554.06		$602.1573	$602.15	$602.15	$602.30