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	$197.59	8.335%	$214.0591	$214.06	$214.05	$214.10
Purchase #2	$154.48	9.178%	$168.6582	$168.66	$168.65	$168.70
Purchase #3	$129.42	10.188%	$142.6053	$142.61	$142.60	$142.60
Purchase #4	$175.26	12.131%	$196.5208	$196.52	$196.50	$196.50
Purchase #5	$92.52	6.868%	$98.8743	$98.87	$98.85	$98.90
Purchase #6	$14.43	7.738%	$15.5466	$15.55	$15.55	$15.50
Purchase #7	$245.70	13.684%	$279.3216	$279.32	$279.30	$279.30
7 purchase totals =	$1,009.40		$1,115.5859	$1,115.59	$1,115.50	$1,115.60