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	$66.39	9.492%	$72.6917	$72.69	$72.70	$72.70
Purchase #2	$156.31	5.240%	$164.5006	$164.50	$164.50	$164.50
Purchase #3	$149.83	12.390%	$168.3939	$168.39	$168.40	$168.40
Purchase #4	$168.90	12.150%	$189.4214	$189.42	$189.40	$189.40
Purchase #5	$127.44	7.745%	$137.3102	$137.31	$137.30	$137.30
Purchase #6	$48.43	8.123%	$52.364	$52.36	$52.35	$52.40
Purchase #7	$142.67	3.340%	$147.4352	$147.44	$147.45	$147.40
7 purchase totals =	$859.97		$932.1170	$932.11	$932.10	$932.10