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	$33.39	4.804%	$34.9941	$34.99	$35.00	$35.00
Purchase #2	$70.73	11.537%	$78.8901	$78.89	$78.90	$78.90
Purchase #3	$51.45	5.853%	$54.4614	$54.46	$54.45	$54.50
Purchase #4	$231.82	6.825%	$247.6417	$247.64	$247.65	$247.60
Purchase #5	$243.57	6.556%	$259.5384	$259.54	$259.55	$259.50
Purchase #6	$143.62	5.150%	$151.0164	$151.02	$151.00	$151.00
Purchase #7	$59.29	5.488%	$62.5438	$62.54	$62.55	$62.50
7 purchase totals =	$833.87		$889.0859	$889.08	$889.10	$889.00