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	$139.66	9.454%	$152.8635	$152.86	$152.85	$152.90
Purchase #2	$163.40	3.651%	$169.3657	$169.37	$169.35	$169.40
Purchase #3	$24.86	13.607%	$28.2427	$28.24	$28.25	$28.20
Purchase #4	$168.92	7.331%	$181.3035	$181.30	$181.30	$181.30
Purchase #5	$234.75	10.710%	$259.8917	$259.89	$259.90	$259.90
Purchase #6	$146.46	3.495%	$151.5788	$151.58	$151.60	$151.60
Purchase #7	$166.34	13.116%	$188.1572	$188.16	$188.15	$188.20
7 purchase totals =	$1,044.39		$1,131.4031	$1,131.40	$1,131.40	$1,131.50