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	$241.81	8.850%	$263.2102	$263.21	$263.20	$263.20
Purchase #2	$162.52	3.823%	$168.7331	$168.73	$168.75	$168.70
Purchase #3	$183.63	8.715%	$199.6334	$199.63	$199.65	$199.60
Purchase #4	$153.56	12.581%	$172.8794	$172.88	$172.90	$172.90
Purchase #5	$39.49	7.864%	$42.5955	$42.60	$42.60	$42.60
Purchase #6	$46.87	3.476%	$48.4992	$48.50	$48.50	$48.50
Purchase #7	$109.77	6.423%	$116.8205	$116.82	$116.80	$116.80
7 purchase totals =	$937.65		$1,012.3713	$1,012.37	$1,012.40	$1,012.30