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	$198.75	3.697%	$206.0978	$206.10	$206.10	$206.10
Purchase #2	$162.63	6.181%	$172.6822	$172.68	$172.70	$172.70
Purchase #3	$35.48	7.308%	$38.0729	$38.07	$38.05	$38.10
Purchase #4	$212.83	4.687%	$222.8053	$222.81	$222.80	$222.80
Purchase #5	$145.35	5.158%	$152.8472	$152.85	$152.85	$152.80
Purchase #6	$233.37	12.121%	$261.6568	$261.66	$261.65	$261.70
Purchase #7	$230.97	5.784%	$244.3293	$244.33	$244.35	$244.30
7 purchase totals =	$1,219.38		$1,298.4915	$1,298.50	$1,298.50	$1,298.50