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	$105.77	4.290%	$110.3075	$110.31	$110.30	$110.30
Purchase #2	$63.64	3.419%	$65.8159	$65.82	$65.80	$65.80
Purchase #3	$206.31	4.517%	$215.629	$215.63	$215.65	$215.60
Purchase #4	$45.93	12.782%	$51.8008	$51.80	$51.80	$51.80
Purchase #5	$155.83	10.146%	$171.6405	$171.64	$171.65	$171.60
Purchase #6	$138.48	5.791%	$146.4994	$146.50	$146.50	$146.50
Purchase #7	$177.32	12.111%	$198.7952	$198.80	$198.80	$198.80
7 purchase totals =	$893.28		$960.4883	$960.50	$960.50	$960.40