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	$84.90	13.693%	$96.5254	$96.53	$96.55	$96.50
Purchase #2	$143.52	4.561%	$150.0659	$150.07	$150.05	$150.10
Purchase #3	$59.78	12.817%	$67.442	$67.44	$67.45	$67.40
Purchase #4	$185.76	3.688%	$192.6108	$192.61	$192.60	$192.60
Purchase #5	$173.65	10.120%	$191.2234	$191.22	$191.20	$191.20
Purchase #6	$245.84	13.752%	$279.6479	$279.65	$279.65	$279.60
Purchase #7	$166.63	13.766%	$189.5683	$189.57	$189.55	$189.60
7 purchase totals =	$1,060.08		$1,167.0837	$1,167.09	$1,167.05	$1,167.00