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	$168.44	13.575%	$191.3057	$191.31	$191.30	$191.30
Purchase #2	$156.42	11.585%	$174.5413	$174.54	$174.55	$174.50
Purchase #3	$143.43	11.859%	$160.4394	$160.44	$160.45	$160.40
Purchase #4	$38.93	7.660%	$41.912	$41.91	$41.90	$41.90
Purchase #5	$230.77	4.262%	$240.6054	$240.61	$240.60	$240.60
Purchase #6	$201.30	4.866%	$211.0953	$211.10	$211.10	$211.10
Purchase #7	$113.65	8.801%	$123.6523	$123.65	$123.65	$123.70
7 purchase totals =	$1,052.94		$1,143.5514	$1,143.56	$1,143.55	$1,143.50