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	$78.70	5.281%	$82.8561	$82.86	$82.85	$82.90
Purchase #2	$162.99	12.808%	$183.8658	$183.87	$183.85	$183.90
Purchase #3	$181.83	8.266%	$196.8601	$196.86	$196.85	$196.90
Purchase #4	$38.95	7.416%	$41.8385	$41.84	$41.85	$41.80
Purchase #5	$39.34	5.346%	$41.4431	$41.44	$41.45	$41.40
Purchase #6	$243.52	4.348%	$254.1082	$254.11	$254.10	$254.10
Purchase #7	$217.29	7.530%	$233.6519	$233.65	$233.65	$233.70
7 purchase totals =	$962.62		$1,034.6237	$1,034.63	$1,034.60	$1,034.70