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	$145.93	10.749%	$161.616	$161.62	$161.60	$161.60
Purchase #2	$51.29	10.123%	$56.4821	$56.48	$56.50	$56.50
Purchase #3	$41.44	10.640%	$45.8492	$45.85	$45.85	$45.80
Purchase #4	$198.50	10.709%	$219.7574	$219.76	$219.75	$219.80
Purchase #5	$200.53	7.432%	$215.4334	$215.43	$215.45	$215.40
Purchase #6	$169.65	10.393%	$187.2817	$187.28	$187.30	$187.30
Purchase #7	$86.64	4.181%	$90.2624	$90.26	$90.25	$90.30
7 purchase totals =	$893.98		$976.6822	$976.68	$976.70	$976.70