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	$239.88	6.328%	$255.0596	$255.06	$255.05	$255.10
Purchase #2	$135.38	6.356%	$143.9848	$143.98	$144.00	$144.00
Purchase #3	$149.56	13.263%	$169.3961	$169.40	$169.40	$169.40
Purchase #4	$181.83	3.686%	$188.5323	$188.53	$188.55	$188.50
Purchase #5	$78.98	5.253%	$83.1288	$83.13	$83.15	$83.10
Purchase #6	$159.90	7.692%	$172.1995	$172.20	$172.20	$172.20
Purchase #7	$31.59	7.871%	$34.0764	$34.08	$34.10	$34.10
7 purchase totals =	$977.12		$1,046.3775	$1,046.38	$1,046.45	$1,046.40