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	$164.89	8.396%	$178.7342	$178.73	$178.75	$178.70
Purchase #2	$204.68	8.211%	$221.4863	$221.49	$221.50	$221.50
Purchase #3	$212.88	6.415%	$226.5363	$226.54	$226.55	$226.50
Purchase #4	$58.33	7.313%	$62.5957	$62.60	$62.60	$62.60
Purchase #5	$112.38	5.645%	$118.7239	$118.72	$118.70	$118.70
Purchase #6	$46.41	11.184%	$51.6005	$51.60	$51.60	$51.60
Purchase #7	$244.38	11.261%	$271.8996	$271.90	$271.90	$271.90
7 purchase totals =	$1,043.95		$1,131.5765	$1,131.58	$1,131.60	$1,131.50