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	$106.48	11.301%	$118.5133	$118.51	$118.50	$118.50
Purchase #2	$94.52	4.418%	$98.6959	$98.70	$98.70	$98.70
Purchase #3	$248.73	12.124%	$278.886	$278.89	$278.90	$278.90
Purchase #4	$40.34	7.225%	$43.2546	$43.25	$43.25	$43.30
Purchase #5	$226.87	5.736%	$239.8833	$239.88	$239.90	$239.90
Purchase #6	$205.44	8.801%	$223.5208	$223.52	$223.50	$223.50
Purchase #7	$10.35	10.544%	$11.4413	$11.44	$11.45	$11.40
7 purchase totals =	$932.73		$1,014.1952	$1,014.19	$1,014.20	$1,014.20