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	$52.65	3.790%	$54.6454	$54.65	$54.65	$54.60
Purchase #2	$10.41	3.568%	$10.7814	$10.78	$10.80	$10.80
Purchase #3	$84.60	13.689%	$96.1809	$96.18	$96.20	$96.20
Purchase #4	$72.92	6.775%	$77.8603	$77.86	$77.85	$77.90
Purchase #5	$114.87	4.109%	$119.59	$119.59	$119.60	$119.60
Purchase #6	$163.62	10.204%	$180.3158	$180.32	$180.30	$180.30
Purchase #7	$42.60	11.826%	$47.6379	$47.64	$47.65	$47.60
7 purchase totals =	$541.67		$587.0117	$587.02	$587.05	$587.00