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	$171.37	4.775%	$179.5529	$179.55	$179.55	$179.60
Purchase #2	$122.74	13.372%	$139.1528	$139.15	$139.15	$139.20
Purchase #3	$106.52	9.216%	$116.3369	$116.34	$116.35	$116.30
Purchase #4	$206.25	9.382%	$225.6004	$225.60	$225.60	$225.60
Purchase #5	$231.41	12.454%	$260.2298	$260.23	$260.25	$260.20
Purchase #6	$88.46	3.555%	$91.6048	$91.60	$91.60	$91.60
Purchase #7	$48.55	13.632%	$55.1683	$55.17	$55.15	$55.20
7 purchase totals =	$975.30		$1,067.6459	$1,067.64	$1,067.65	$1,067.70