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	$241.48	11.610%	$269.5158	$269.52	$269.50	$269.50
Purchase #2	$73.95	11.149%	$82.1947	$82.19	$82.20	$82.20
Purchase #3	$124.51	12.195%	$139.694	$139.69	$139.70	$139.70
Purchase #4	$65.75	10.855%	$72.8872	$72.89	$72.90	$72.90
Purchase #5	$51.74	9.683%	$56.75	$56.75	$56.75	$56.80
Purchase #6	$167.49	4.703%	$175.3671	$175.37	$175.35	$175.40
Purchase #7	$193.42	7.193%	$207.3327	$207.33	$207.35	$207.30
7 purchase totals =	$918.34		$1,003.7415	$1,003.74	$1,003.75	$1,003.80