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	$240.82	13.595%	$273.5595	$273.56	$273.55	$273.60
Purchase #2	$247.26	7.714%	$266.3336	$266.33	$266.35	$266.30
Purchase #3	$47.40	7.320%	$50.8697	$50.87	$50.85	$50.90
Purchase #4	$176.66	10.111%	$194.5221	$194.52	$194.50	$194.50
Purchase #5	$49.87	5.295%	$52.5106	$52.51	$52.50	$52.50
Purchase #6	$50.74	11.850%	$56.7527	$56.75	$56.75	$56.80
Purchase #7	$182.57	5.363%	$192.3612	$192.36	$192.35	$192.40
7 purchase totals =	$995.32		$1,086.9094	$1,086.90	$1,086.85	$1,087.00