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	$203.73	6.541%	$217.056	$217.06	$217.05	$217.10
Purchase #2	$196.63	7.195%	$210.7775	$210.78	$210.80	$210.80
Purchase #3	$35.50	5.300%	$37.3815	$37.38	$37.40	$37.40
Purchase #4	$129.65	12.452%	$145.794	$145.79	$145.80	$145.80
Purchase #5	$166.60	3.542%	$172.501	$172.50	$172.50	$172.50
Purchase #6	$189.94	10.781%	$210.4174	$210.42	$210.40	$210.40
Purchase #7	$58.55	10.763%	$64.8517	$64.85	$64.85	$64.90
7 purchase totals =	$980.60		$1,058.7791	$1,058.78	$1,058.80	$1,058.90