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	$207.69	5.659%	$219.4432	$219.44	$219.45	$219.40
Purchase #2	$237.85	10.492%	$262.8052	$262.81	$262.80	$262.80
Purchase #3	$67.99	3.489%	$70.3622	$70.36	$70.35	$70.40
Purchase #4	$190.50	9.218%	$208.0603	$208.06	$208.05	$208.10
Purchase #5	$52.78	13.284%	$59.7913	$59.79	$59.80	$59.80
Purchase #6	$194.79	13.721%	$221.5171	$221.52	$221.50	$221.50
Purchase #7	$96.83	7.735%	$104.3198	$104.32	$104.30	$104.30
7 purchase totals =	$1,048.43		$1,146.2991	$1,146.30	$1,146.25	$1,146.30