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	$156.55	7.859%	$168.8533	$168.85	$168.85	$168.90
Purchase #2	$115.28	11.375%	$128.3931	$128.39	$128.40	$128.40
Purchase #3	$205.69	12.466%	$231.3313	$231.33	$231.35	$231.30
Purchase #4	$133.52	4.614%	$139.6806	$139.68	$139.70	$139.70
Purchase #5	$81.75	8.420%	$88.6334	$88.63	$88.65	$88.60
Purchase #6	$160.38	7.438%	$172.3091	$172.31	$172.30	$172.30
Purchase #7	$116.42	3.724%	$120.7555	$120.76	$120.75	$120.80
7 purchase totals =	$969.59		$1,049.9563	$1,049.95	$1,050.00	$1,050.00