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	$220.57	4.248%	$229.9398	$229.94	$229.95	$229.90
Purchase #2	$121.67	8.120%	$131.5496	$131.55	$131.55	$131.50
Purchase #3	$43.92	7.676%	$47.2913	$47.29	$47.30	$47.30
Purchase #4	$212.54	4.213%	$221.4943	$221.49	$221.50	$221.50
Purchase #5	$234.96	11.700%	$262.4503	$262.45	$262.45	$262.50
Purchase #6	$87.93	9.746%	$96.4997	$96.50	$96.50	$96.50
Purchase #7	$68.31	4.571%	$71.4325	$71.43	$71.45	$71.40
7 purchase totals =	$989.90		$1,060.6575	$1,060.65	$1,060.70	$1,060.60