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	$182.94	11.138%	$203.3159	$203.32	$203.30	$203.30
Purchase #2	$205.53	10.701%	$227.5238	$227.52	$227.50	$227.50
Purchase #3	$50.89	10.787%	$56.3795	$56.38	$56.40	$56.40
Purchase #4	$28.63	11.475%	$31.9153	$31.92	$31.90	$31.90
Purchase #5	$10.47	12.259%	$11.7535	$11.75	$11.75	$11.80
Purchase #6	$247.98	9.416%	$271.3298	$271.33	$271.35	$271.30
Purchase #7	$186.94	7.197%	$200.3941	$200.39	$200.40	$200.40
7 purchase totals =	$913.38		$1,002.6119	$1,002.61	$1,002.60	$1,002.60