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	$36.93	11.708%	$41.2538	$41.25	$41.25	$41.30
Purchase #2	$98.30	5.348%	$103.5571	$103.56	$103.55	$103.60
Purchase #3	$42.49	7.687%	$45.7562	$45.76	$45.75	$45.80
Purchase #4	$108.69	4.120%	$113.168	$113.17	$113.15	$113.20
Purchase #5	$151.86	13.179%	$171.8736	$171.87	$171.85	$171.90
Purchase #6	$36.60	5.589%	$38.6456	$38.65	$38.65	$38.60
Purchase #7	$55.45	12.658%	$62.4689	$62.47	$62.45	$62.50
7 purchase totals =	$530.32		$576.7232	$576.73	$576.65	$576.90