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	$89.89	3.438%	$92.9804	$92.98	$93.00	$93.00
Purchase #2	$181.59	13.229%	$205.6125	$205.61	$205.60	$205.60
Purchase #3	$157.29	13.173%	$178.0098	$178.01	$178.00	$178.00
Purchase #4	$173.36	5.393%	$182.7093	$182.71	$182.70	$182.70
Purchase #5	$12.45	6.528%	$13.2627	$13.26	$13.25	$13.30
Purchase #6	$191.77	7.371%	$205.9054	$205.91	$205.90	$205.90
Purchase #7	$117.39	12.306%	$131.836	$131.84	$131.85	$131.80
7 purchase totals =	$923.74		$1,010.3161	$1,010.32	$1,010.30	$1,010.30