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	$13.63	13.625%	$15.4871	$15.49	$15.50	$15.50
Purchase #2	$232.73	4.447%	$243.0795	$243.08	$243.10	$243.10
Purchase #3	$150.29	12.849%	$169.6008	$169.60	$169.60	$169.60
Purchase #4	$241.30	3.797%	$250.4622	$250.46	$250.45	$250.50
Purchase #5	$53.44	10.451%	$59.025	$59.03	$59.05	$59.00
Purchase #6	$142.86	5.308%	$150.443	$150.44	$150.45	$150.40
Purchase #7	$210.73	11.805%	$235.6067	$235.61	$235.60	$235.60
7 purchase totals =	$1,044.98		$1,123.7043	$1,123.71	$1,123.75	$1,123.70