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	$240.66	11.140%	$267.4695	$267.47	$267.45	$267.50
Purchase #2	$93.70	3.264%	$96.7584	$96.76	$96.75	$96.80
Purchase #3	$130.77	10.697%	$144.7585	$144.76	$144.75	$144.80
Purchase #4	$220.72	5.761%	$233.4357	$233.44	$233.45	$233.40
Purchase #5	$75.77	12.318%	$85.1033	$85.10	$85.10	$85.10
Purchase #6	$226.36	6.740%	$241.6167	$241.62	$241.60	$241.60
Purchase #7	$54.54	12.577%	$61.3995	$61.40	$61.40	$61.40
7 purchase totals =	$1,042.52		$1,130.5416	$1,130.55	$1,130.50	$1,130.60