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	$200.38	5.689%	$211.7796	$211.78	$211.80	$211.80
Purchase #2	$146.77	12.343%	$164.8858	$164.89	$164.90	$164.90
Purchase #3	$194.49	8.123%	$210.2884	$210.29	$210.30	$210.30
Purchase #4	$75.98	3.657%	$78.7586	$78.76	$78.75	$78.80
Purchase #5	$111.74	12.286%	$125.4684	$125.47	$125.45	$125.50
Purchase #6	$62.42	5.337%	$65.7514	$65.75	$65.75	$65.80
Purchase #7	$101.83	5.551%	$107.4826	$107.48	$107.50	$107.50
7 purchase totals =	$893.61		$964.4148	$964.42	$964.45	$964.60