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	$161.55	11.607%	$180.3011	$180.30	$180.30	$180.30
Purchase #2	$20.83	3.480%	$21.5549	$21.55	$21.55	$21.60
Purchase #3	$98.38	4.859%	$103.1603	$103.16	$103.15	$103.20
Purchase #4	$150.54	10.154%	$165.8258	$165.83	$165.85	$165.80
Purchase #5	$24.27	5.849%	$25.6896	$25.69	$25.70	$25.70
Purchase #6	$180.34	11.132%	$200.4154	$200.42	$200.40	$200.40
Purchase #7	$233.97	7.638%	$251.8406	$251.84	$251.85	$251.80
7 purchase totals =	$869.88		$948.7877	$948.79	$948.80	$948.80