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	$70.96	10.585%	$78.4711	$78.47	$78.45	$78.50
Purchase #2	$119.82	11.618%	$133.7407	$133.74	$133.75	$133.70
Purchase #3	$42.75	6.670%	$45.6014	$45.60	$45.60	$45.60
Purchase #4	$133.27	4.722%	$139.563	$139.56	$139.55	$139.60
Purchase #5	$240.68	8.418%	$260.9404	$260.94	$260.95	$260.90
Purchase #6	$44.65	3.577%	$46.2471	$46.25	$46.25	$46.20
Purchase #7	$79.66	3.478%	$82.4306	$82.43	$82.45	$82.40
7 purchase totals =	$731.79		$786.9943	$786.99	$787.00	$786.90