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	$241.64	11.269%	$268.8704	$268.87	$268.85	$268.90
Purchase #2	$207.84	6.859%	$222.0957	$222.10	$222.10	$222.10
Purchase #3	$78.25	13.298%	$88.6557	$88.66	$88.65	$88.70
Purchase #4	$239.79	11.718%	$267.8886	$267.89	$267.90	$267.90
Purchase #5	$151.82	13.221%	$171.8921	$171.89	$171.90	$171.90
Purchase #6	$110.26	8.740%	$119.8967	$119.90	$119.90	$119.90
Purchase #7	$177.58	4.492%	$185.5569	$185.56	$185.55	$185.60
7 purchase totals =	$1,207.18		$1,324.8561	$1,324.87	$1,324.85	$1,325.00