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	$167.39	7.560%	$180.0447	$180.04	$180.05	$180.00
Purchase #2	$187.80	10.624%	$207.7519	$207.75	$207.75	$207.80
Purchase #3	$38.98	8.802%	$42.411	$42.41	$42.40	$42.40
Purchase #4	$118.60	5.113%	$124.664	$124.66	$124.65	$124.70
Purchase #5	$41.77	9.115%	$45.5773	$45.58	$45.60	$45.60
Purchase #6	$186.40	7.528%	$200.4322	$200.43	$200.45	$200.40
Purchase #7	$148.33	10.760%	$164.2903	$164.29	$164.30	$164.30
7 purchase totals =	$889.27		$965.1714	$965.16	$965.20	$965.20