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	$235.99	3.745%	$244.8278	$244.83	$244.85	$244.80
Purchase #2	$40.47	12.640%	$45.5854	$45.59	$45.60	$45.60
Purchase #3	$45.97	6.753%	$49.0744	$49.07	$49.05	$49.10
Purchase #4	$133.35	7.154%	$142.8899	$142.89	$142.90	$142.90
Purchase #5	$186.61	5.521%	$196.9127	$196.91	$196.90	$196.90
Purchase #6	$208.72	9.381%	$228.3	$228.30	$228.30	$228.30
Purchase #7	$53.28	7.107%	$57.0666	$57.07	$57.05	$57.10
7 purchase totals =	$904.39		$964.6568	$964.66	$964.65	$964.70