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	$162.69	13.754%	$185.0664	$185.07	$185.05	$185.10
Purchase #2	$53.91	9.791%	$59.1883	$59.19	$59.20	$59.20
Purchase #3	$55.90	3.524%	$57.8699	$57.87	$57.85	$57.90
Purchase #4	$85.40	11.116%	$94.8931	$94.89	$94.90	$94.90
Purchase #5	$227.31	12.547%	$255.8306	$255.83	$255.85	$255.80
Purchase #6	$89.29	3.732%	$92.6223	$92.62	$92.60	$92.60
Purchase #7	$168.25	9.493%	$184.222	$184.22	$184.20	$184.20
7 purchase totals =	$842.75		$929.6926	$929.69	$929.65	$929.70