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	$126.54	6.645%	$134.9486	$134.95	$134.95	$134.90
Purchase #2	$86.81	13.849%	$98.8323	$98.83	$98.85	$98.80
Purchase #3	$35.69	10.424%	$39.4103	$39.41	$39.40	$39.40
Purchase #4	$141.39	10.145%	$155.734	$155.73	$155.75	$155.70
Purchase #5	$117.35	5.203%	$123.4557	$123.46	$123.45	$123.50
Purchase #6	$97.45	11.397%	$108.5564	$108.56	$108.55	$108.60
Purchase #7	$63.98	13.204%	$72.4279	$72.43	$72.45	$72.40
7 purchase totals =	$669.21		$733.3652	$733.37	$733.40	$733.30