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	$90.61	11.853%	$101.35	$101.35	$101.35	$101.40
Purchase #2	$118.80	8.337%	$128.7044	$128.70	$128.70	$128.70
Purchase #3	$172.63	4.356%	$180.1498	$180.15	$180.15	$180.10
Purchase #4	$179.91	4.340%	$187.7181	$187.72	$187.70	$187.70
Purchase #5	$221.91	8.419%	$240.5926	$240.59	$240.60	$240.60
Purchase #6	$135.42	7.132%	$145.0782	$145.08	$145.10	$145.10
Purchase #7	$178.79	9.726%	$196.1791	$196.18	$196.20	$196.20
7 purchase totals =	$1,098.07		$1,179.7722	$1,179.77	$1,179.80	$1,179.80