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	$84.35	9.442%	$92.3143	$92.31	$92.30	$92.30
Purchase #2	$148.49	10.781%	$164.4987	$164.50	$164.50	$164.50
Purchase #3	$243.90	5.820%	$258.095	$258.10	$258.10	$258.10
Purchase #4	$38.58	6.140%	$40.9488	$40.95	$40.95	$40.90
Purchase #5	$153.81	7.824%	$165.8441	$165.84	$165.85	$165.80
Purchase #6	$35.73	8.417%	$38.7374	$38.74	$38.75	$38.70
Purchase #7	$234.61	6.204%	$249.1652	$249.17	$249.15	$249.20
7 purchase totals =	$939.47		$1,009.6035	$1,009.61	$1,009.60	$1,009.50