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	$101.30	9.703%	$111.1291	$111.13	$111.15	$111.10
Purchase #2	$198.54	5.775%	$210.0057	$210.01	$210.00	$210.00
Purchase #3	$130.41	10.837%	$144.5425	$144.54	$144.55	$144.50
Purchase #4	$232.67	6.790%	$248.4683	$248.47	$248.45	$248.50
Purchase #5	$163.97	6.427%	$174.5084	$174.51	$174.50	$174.50
Purchase #6	$82.39	13.854%	$93.8043	$93.80	$93.80	$93.80
Purchase #7	$40.28	6.607%	$42.9413	$42.94	$42.95	$42.90
7 purchase totals =	$949.56		$1,025.3996	$1,025.40	$1,025.40	$1,025.30