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	$246.32	6.734%	$262.9072	$262.91	$262.90	$262.90
Purchase #2	$111.87	5.732%	$118.2824	$118.28	$118.30	$118.30
Purchase #3	$248.59	5.586%	$262.4762	$262.48	$262.50	$262.50
Purchase #4	$147.86	3.166%	$152.5412	$152.54	$152.55	$152.50
Purchase #5	$40.76	7.840%	$43.9556	$43.96	$43.95	$44.00
Purchase #6	$116.72	8.414%	$126.5408	$126.54	$126.55	$126.50
Purchase #7	$149.73	12.729%	$168.7891	$168.79	$168.80	$168.80
7 purchase totals =	$1,061.85		$1,135.4925	$1,135.50	$1,135.55	$1,135.50