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	$77.85	7.713%	$83.8546	$83.85	$83.85	$83.90
Purchase #2	$83.51	9.643%	$91.5629	$91.56	$91.55	$91.60
Purchase #3	$139.76	3.462%	$144.5985	$144.60	$144.60	$144.60
Purchase #4	$36.92	3.521%	$38.22	$38.22	$38.20	$38.20
Purchase #5	$208.86	4.234%	$217.7031	$217.70	$217.70	$217.70
Purchase #6	$94.98	10.818%	$105.2549	$105.25	$105.25	$105.30
Purchase #7	$166.48	9.865%	$182.9033	$182.90	$182.90	$182.90
7 purchase totals =	$808.36		$864.0973	$864.08	$864.05	$864.20