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	$221.36	10.410%	$244.4036	$244.40	$244.40	$244.40
Purchase #2	$118.70	7.745%	$127.8933	$127.89	$127.90	$127.90
Purchase #3	$67.54	3.228%	$69.7202	$69.72	$69.70	$69.70
Purchase #4	$113.72	11.674%	$126.9957	$127.00	$127.00	$127.00
Purchase #5	$201.59	9.184%	$220.104	$220.10	$220.10	$220.10
Purchase #6	$231.65	7.866%	$249.8716	$249.87	$249.85	$249.90
Purchase #7	$101.94	10.184%	$112.3216	$112.32	$112.30	$112.30
7 purchase totals =	$1,056.50		$1,151.3100	$1,151.30	$1,151.25	$1,151.30