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	$189.83	11.259%	$211.203	$211.20	$211.20	$211.20
Purchase #2	$70.78	10.820%	$78.4384	$78.44	$78.45	$78.40
Purchase #3	$195.73	6.313%	$208.0864	$208.09	$208.10	$208.10
Purchase #4	$240.55	8.241%	$260.3737	$260.37	$260.35	$260.40
Purchase #5	$67.65	5.509%	$71.3768	$71.38	$71.40	$71.40
Purchase #6	$88.32	11.466%	$98.4468	$98.45	$98.45	$98.40
Purchase #7	$54.85	7.818%	$59.1382	$59.14	$59.15	$59.10
7 purchase totals =	$907.71		$987.0633	$987.07	$987.10	$987.00