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	$136.28	4.664%	$142.6361	$142.64	$142.65	$142.60
Purchase #2	$46.37	10.873%	$51.4118	$51.41	$51.40	$51.40
Purchase #3	$163.42	7.396%	$175.5065	$175.51	$175.50	$175.50
Purchase #4	$62.94	7.248%	$67.5019	$67.50	$67.50	$67.50
Purchase #5	$18.54	8.632%	$20.1404	$20.14	$20.15	$20.10
Purchase #6	$199.25	5.107%	$209.4257	$209.43	$209.45	$209.40
Purchase #7	$59.31	8.706%	$64.4735	$64.47	$64.45	$64.50
7 purchase totals =	$686.11		$731.0959	$731.10	$731.10	$731.00