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	$108.28	7.731%	$116.6511	$116.65	$116.65	$116.70
Purchase #2	$62.52	13.395%	$70.8946	$70.89	$70.90	$70.90
Purchase #3	$246.44	8.503%	$267.3948	$267.39	$267.40	$267.40
Purchase #4	$43.83	7.510%	$47.1216	$47.12	$47.10	$47.10
Purchase #5	$157.56	4.248%	$164.2531	$164.25	$164.25	$164.30
Purchase #6	$72.85	7.483%	$78.3014	$78.30	$78.30	$78.30
Purchase #7	$41.47	11.397%	$46.1963	$46.20	$46.20	$46.20
7 purchase totals =	$732.95		$790.8129	$790.80	$790.80	$790.90