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	$111.99	11.319%	$124.6661	$124.67	$124.65	$124.70
Purchase #2	$176.56	13.639%	$200.641	$200.64	$200.65	$200.60
Purchase #3	$248.88	9.158%	$271.6724	$271.67	$271.65	$271.70
Purchase #4	$48.72	5.802%	$51.5467	$51.55	$51.55	$51.50
Purchase #5	$179.97	3.845%	$186.8898	$186.89	$186.90	$186.90
Purchase #6	$105.50	3.628%	$109.3275	$109.33	$109.35	$109.30
Purchase #7	$164.82	13.172%	$186.5301	$186.53	$186.55	$186.50
7 purchase totals =	$1,036.44		$1,131.2736	$1,131.28	$1,131.30	$1,131.20