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	$216.77	5.399%	$228.4734	$228.47	$228.45	$228.50
Purchase #2	$190.66	13.352%	$216.1169	$216.12	$216.10	$216.10
Purchase #3	$40.89	6.438%	$43.5225	$43.52	$43.50	$43.50
Purchase #4	$56.76	4.349%	$59.2285	$59.23	$59.25	$59.20
Purchase #5	$71.70	5.835%	$75.8837	$75.88	$75.90	$75.90
Purchase #6	$136.85	5.458%	$144.3193	$144.32	$144.30	$144.30
Purchase #7	$56.26	4.744%	$58.929	$58.93	$58.95	$58.90
7 purchase totals =	$769.89		$826.4733	$826.47	$826.45	$826.40