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	$139.56	9.721%	$153.1266	$153.13	$153.15	$153.10
Purchase #2	$207.51	9.680%	$227.597	$227.60	$227.60	$227.60
Purchase #3	$46.78	9.478%	$51.2138	$51.21	$51.20	$51.20
Purchase #4	$222.80	4.755%	$233.3941	$233.39	$233.40	$233.40
Purchase #5	$142.80	6.658%	$152.3076	$152.31	$152.30	$152.30
Purchase #6	$234.94	10.461%	$259.5171	$259.52	$259.50	$259.50
Purchase #7	$37.29	5.817%	$39.4592	$39.46	$39.45	$39.50
7 purchase totals =	$1,031.68		$1,116.6154	$1,116.62	$1,116.60	$1,116.60