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	$165.86	8.277%	$179.5882	$179.59	$179.60	$179.60
Purchase #2	$166.44	3.700%	$172.5983	$172.60	$172.60	$172.60
Purchase #3	$187.25	13.129%	$211.8341	$211.83	$211.85	$211.80
Purchase #4	$54.73	12.589%	$61.62	$61.62	$61.60	$61.60
Purchase #5	$43.42	3.610%	$44.9875	$44.99	$45.00	$45.00
Purchase #6	$119.59	3.144%	$123.3499	$123.35	$123.35	$123.30
Purchase #7	$13.82	3.102%	$14.2487	$14.25	$14.25	$14.20
7 purchase totals =	$751.11		$808.2267	$808.23	$808.25	$808.10