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	$118.72	13.461%	$134.7009	$134.70	$134.70	$134.70
Purchase #2	$93.90	3.125%	$96.8344	$96.83	$96.85	$96.80
Purchase #3	$188.96	5.141%	$198.6744	$198.67	$198.65	$198.70
Purchase #4	$81.39	6.857%	$86.9709	$86.97	$86.95	$87.00
Purchase #5	$191.71	4.474%	$200.2871	$200.29	$200.30	$200.30
Purchase #6	$171.43	10.156%	$188.8404	$188.84	$188.85	$188.80
Purchase #7	$95.33	8.668%	$103.5932	$103.59	$103.60	$103.60
7 purchase totals =	$941.44		$1,009.9013	$1,009.89	$1,009.90	$1,009.90