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	$239.54	3.416%	$247.7227	$247.72	$247.70	$247.70
Purchase #2	$159.50	10.240%	$175.8328	$175.83	$175.85	$175.80
Purchase #3	$97.65	3.252%	$100.8256	$100.83	$100.85	$100.80
Purchase #4	$12.93	12.827%	$14.5885	$14.59	$14.60	$14.60
Purchase #5	$85.77	4.154%	$89.3329	$89.33	$89.35	$89.30
Purchase #6	$249.91	7.153%	$267.7861	$267.79	$267.80	$267.80
Purchase #7	$25.85	8.122%	$27.9495	$27.95	$27.95	$27.90
7 purchase totals =	$871.15		$924.0381	$924.04	$924.10	$923.90