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	$85.47	4.849%	$89.6144	$89.61	$89.60	$89.60
Purchase #2	$232.86	4.468%	$243.2642	$243.26	$243.25	$243.30
Purchase #3	$38.65	10.561%	$42.7318	$42.73	$42.75	$42.70
Purchase #4	$240.52	13.459%	$272.8916	$272.89	$272.90	$272.90
Purchase #5	$206.40	4.303%	$215.2814	$215.28	$215.30	$215.30
Purchase #6	$188.44	9.315%	$205.9932	$205.99	$206.00	$206.00
Purchase #7	$166.80	13.510%	$189.3347	$189.33	$189.35	$189.30
7 purchase totals =	$1,159.14		$1,259.1113	$1,259.09	$1,259.15	$1,259.10