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	$114.79	10.214%	$126.5147	$126.51	$126.50	$126.50
Purchase #2	$118.59	6.340%	$126.1086	$126.11	$126.10	$126.10
Purchase #3	$18.61	10.846%	$20.6284	$20.63	$20.65	$20.60
Purchase #4	$142.74	3.141%	$147.2235	$147.22	$147.20	$147.20
Purchase #5	$166.47	6.402%	$177.1274	$177.13	$177.15	$177.10
Purchase #6	$79.42	12.526%	$89.3681	$89.37	$89.35	$89.40
Purchase #7	$65.31	11.570%	$72.8664	$72.87	$72.85	$72.90
7 purchase totals =	$705.93		$759.8371	$759.84	$759.80	$759.80