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	$23.37	10.266%	$25.7692	$25.77	$25.75	$25.80
Purchase #2	$19.32	10.314%	$21.3127	$21.31	$21.30	$21.30
Purchase #3	$5.26	3.808%	$5.4603	$5.46	$5.45	$5.50
Purchase #4	$88.41	5.440%	$93.2195	$93.22	$93.20	$93.20
Purchase #5	$141.52	5.175%	$148.8437	$148.84	$148.85	$148.80
Purchase #6	$71.82	9.623%	$78.7312	$78.73	$78.75	$78.70
Purchase #7	$134.37	13.510%	$152.5234	$152.52	$152.50	$152.50
7 purchase totals =	$484.07		$525.8600	$525.85	$525.80	$525.80