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	$240.62	7.170%	$257.8725	$257.87	$257.85	$257.90
Purchase #2	$41.93	9.395%	$45.8693	$45.87	$45.85	$45.90
Purchase #3	$86.61	4.512%	$90.5178	$90.52	$90.50	$90.50
Purchase #4	$71.48	5.534%	$75.4357	$75.44	$75.45	$75.40
Purchase #5	$186.67	4.743%	$195.5238	$195.52	$195.50	$195.50
Purchase #6	$216.84	13.620%	$246.3736	$246.37	$246.35	$246.40
Purchase #7	$157.34	11.428%	$175.3208	$175.32	$175.30	$175.30
7 purchase totals =	$1,001.49		$1,086.9135	$1,086.91	$1,086.80	$1,086.90