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	$101.29	12.846%	$114.3017	$114.30	$114.30	$114.30
Purchase #2	$221.77	7.459%	$238.3118	$238.31	$238.30	$238.30
Purchase #3	$126.84	3.383%	$131.131	$131.13	$131.15	$131.10
Purchase #4	$162.66	5.722%	$171.9674	$171.97	$171.95	$172.00
Purchase #5	$99.67	9.796%	$109.4337	$109.43	$109.45	$109.40
Purchase #6	$228.87	4.273%	$238.6496	$238.65	$238.65	$238.60
Purchase #7	$6.54	3.231%	$6.7513	$6.75	$6.75	$6.80
7 purchase totals =	$947.64		$1,010.5465	$1,010.54	$1,010.55	$1,010.50