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	$120.34	9.209%	$131.4221	$131.42	$131.40	$131.40
Purchase #2	$76.28	5.472%	$80.454	$80.45	$80.45	$80.50
Purchase #3	$129.65	13.690%	$147.3991	$147.40	$147.40	$147.40
Purchase #4	$221.62	13.331%	$251.1642	$251.16	$251.15	$251.20
Purchase #5	$184.94	13.693%	$210.2638	$210.26	$210.25	$210.30
Purchase #6	$84.56	7.139%	$90.5967	$90.60	$90.60	$90.60
Purchase #7	$145.62	7.645%	$156.7526	$156.75	$156.75	$156.80
7 purchase totals =	$963.01		$1,068.0525	$1,068.04	$1,068.00	$1,068.20