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	$82.29	11.712%	$91.9278	$91.93	$91.95	$91.90
Purchase #2	$225.32	10.617%	$249.2422	$249.24	$249.25	$249.20
Purchase #3	$116.65	5.690%	$123.2874	$123.29	$123.30	$123.30
Purchase #4	$238.33	7.201%	$255.4921	$255.49	$255.50	$255.50
Purchase #5	$215.61	11.705%	$240.8472	$240.85	$240.85	$240.80
Purchase #6	$164.83	3.780%	$171.0606	$171.06	$171.05	$171.10
Purchase #7	$205.57	6.126%	$218.1632	$218.16	$218.15	$218.20
7 purchase totals =	$1,248.60		$1,350.0205	$1,350.02	$1,350.05	$1,350.00