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	$213.45	4.111%	$222.2249	$222.22	$222.20	$222.20
Purchase #2	$172.80	6.593%	$184.1927	$184.19	$184.20	$184.20
Purchase #3	$67.75	6.691%	$72.2832	$72.28	$72.30	$72.30
Purchase #4	$170.64	13.762%	$194.1235	$194.12	$194.10	$194.10
Purchase #5	$217.51	6.205%	$231.0065	$231.01	$231.00	$231.00
Purchase #6	$201.74	10.345%	$222.61	$222.61	$222.60	$222.60
Purchase #7	$35.42	13.688%	$40.2683	$40.27	$40.25	$40.30
7 purchase totals =	$1,079.31		$1,166.7091	$1,166.70	$1,166.65	$1,166.70