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	$247.68	10.178%	$272.8889	$272.89	$272.90	$272.90
Purchase #2	$173.40	5.140%	$182.3128	$182.31	$182.30	$182.30
Purchase #3	$19.46	11.734%	$21.7434	$21.74	$21.75	$21.70
Purchase #4	$11.96	11.470%	$13.3318	$13.33	$13.35	$13.30
Purchase #5	$233.80	3.801%	$242.6867	$242.69	$242.70	$242.70
Purchase #6	$86.89	5.318%	$91.5108	$91.51	$91.50	$91.50
Purchase #7	$117.71	4.811%	$123.373	$123.37	$123.35	$123.40
7 purchase totals =	$890.90		$947.8474	$947.84	$947.85	$947.80