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	$12.27	11.272%	$13.6531	$13.65	$13.65	$13.70
Purchase #2	$82.66	6.660%	$88.1652	$88.17	$88.15	$88.20
Purchase #3	$163.61	11.822%	$182.952	$182.95	$182.95	$183.00
Purchase #4	$171.51	4.450%	$179.1422	$179.14	$179.15	$179.10
Purchase #5	$138.71	5.490%	$146.3252	$146.33	$146.35	$146.30
Purchase #6	$52.79	7.764%	$56.8886	$56.89	$56.90	$56.90
Purchase #7	$186.51	5.288%	$196.3726	$196.37	$196.35	$196.40
7 purchase totals =	$808.06		$863.4989	$863.50	$863.50	$863.60