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	$154.99	6.349%	$164.8303	$164.83	$164.85	$164.80
Purchase #2	$166.45	7.165%	$178.3761	$178.38	$178.40	$178.40
Purchase #3	$69.78	4.459%	$72.8915	$72.89	$72.90	$72.90
Purchase #4	$195.81	10.388%	$216.1507	$216.15	$216.15	$216.20
Purchase #5	$105.52	3.676%	$109.3989	$109.40	$109.40	$109.40
Purchase #6	$155.40	10.195%	$171.243	$171.24	$171.25	$171.20
Purchase #7	$214.71	8.672%	$233.3297	$233.33	$233.35	$233.30
7 purchase totals =	$1,062.66		$1,146.2202	$1,146.22	$1,146.30	$1,146.20