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	$141.64	4.654%	$148.2319	$148.23	$148.25	$148.20
Purchase #2	$186.49	10.426%	$205.9334	$205.93	$205.95	$205.90
Purchase #3	$21.76	5.318%	$22.9172	$22.92	$22.90	$22.90
Purchase #4	$14.50	9.610%	$15.8935	$15.89	$15.90	$15.90
Purchase #5	$129.88	12.153%	$145.6643	$145.66	$145.65	$145.70
Purchase #6	$159.37	5.208%	$167.67	$167.67	$167.65	$167.70
Purchase #7	$78.63	5.265%	$82.7699	$82.77	$82.75	$82.80
7 purchase totals =	$732.27		$789.0802	$789.07	$789.05	$789.10