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	$205.47	3.831%	$213.3416	$213.34	$213.35	$213.30
Purchase #2	$190.83	5.271%	$200.8886	$200.89	$200.90	$200.90
Purchase #3	$154.42	10.826%	$171.1375	$171.14	$171.15	$171.10
Purchase #4	$238.64	7.360%	$256.2039	$256.20	$256.20	$256.20
Purchase #5	$154.34	7.217%	$165.4787	$165.48	$165.50	$165.50
Purchase #6	$14.73	11.419%	$16.412	$16.41	$16.40	$16.40
Purchase #7	$28.59	9.771%	$31.3835	$31.38	$31.40	$31.40
7 purchase totals =	$987.02		$1,054.8458	$1,054.84	$1,054.90	$1,054.80