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	$101.80	12.868%	$114.8996	$114.90	$114.90	$114.90
Purchase #2	$49.34	9.604%	$54.0786	$54.08	$54.10	$54.10
Purchase #3	$69.83	3.198%	$72.0632	$72.06	$72.05	$72.10
Purchase #4	$212.55	4.229%	$221.5387	$221.54	$221.55	$221.50
Purchase #5	$78.59	4.484%	$82.114	$82.11	$82.10	$82.10
Purchase #6	$195.59	8.717%	$212.6396	$212.64	$212.65	$212.60
Purchase #7	$31.30	3.277%	$32.3257	$32.33	$32.35	$32.30
7 purchase totals =	$739.00		$789.6594	$789.66	$789.70	$789.60