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	$86.61	11.664%	$96.7122	$96.71	$96.70	$96.70
Purchase #2	$78.90	12.287%	$88.5944	$88.59	$88.60	$88.60
Purchase #3	$113.40	9.247%	$123.8861	$123.89	$123.90	$123.90
Purchase #4	$72.27	9.393%	$79.0583	$79.06	$79.05	$79.10
Purchase #5	$244.93	8.214%	$265.0486	$265.05	$265.05	$265.00
Purchase #6	$212.87	7.849%	$229.5782	$229.58	$229.60	$229.60
Purchase #7	$119.57	11.504%	$133.3253	$133.33	$133.35	$133.30
7 purchase totals =	$928.55		$1,016.2031	$1,016.21	$1,016.25	$1,016.20