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	$208.31	5.862%	$220.5211	$220.52	$220.50	$220.50
Purchase #2	$226.46	12.529%	$254.8332	$254.83	$254.85	$254.80
Purchase #3	$80.73	13.552%	$91.6705	$91.67	$91.65	$91.70
Purchase #4	$15.66	13.736%	$17.8111	$17.81	$17.80	$17.80
Purchase #5	$105.96	8.424%	$114.8861	$114.89	$114.90	$114.90
Purchase #6	$221.41	7.627%	$238.2969	$238.30	$238.30	$238.30
Purchase #7	$40.35	7.232%	$43.2681	$43.27	$43.25	$43.30
7 purchase totals =	$898.88		$981.2870	$981.29	$981.25	$981.30