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	$189.65	8.740%	$206.2254	$206.23	$206.25	$206.20
Purchase #2	$161.52	6.569%	$172.1302	$172.13	$172.15	$172.10
Purchase #3	$126.82	7.455%	$136.2744	$136.27	$136.25	$136.30
Purchase #4	$101.83	7.381%	$109.3461	$109.35	$109.35	$109.30
Purchase #5	$222.72	8.354%	$241.326	$241.33	$241.35	$241.30
Purchase #6	$107.34	12.548%	$120.809	$120.81	$120.80	$120.80
Purchase #7	$104.49	9.191%	$114.0937	$114.09	$114.10	$114.10
7 purchase totals =	$1,014.37		$1,100.2048	$1,100.21	$1,100.25	$1,100.10