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	$135.77	12.103%	$152.2022	$152.20	$152.20	$152.20
Purchase #2	$148.54	13.413%	$168.4637	$168.46	$168.45	$168.50
Purchase #3	$90.96	5.740%	$96.1811	$96.18	$96.20	$96.20
Purchase #4	$186.74	9.386%	$204.2674	$204.27	$204.25	$204.30
Purchase #5	$94.54	11.462%	$105.3762	$105.38	$105.40	$105.40
Purchase #6	$202.49	12.231%	$227.2566	$227.26	$227.25	$227.30
Purchase #7	$145.31	13.264%	$164.5839	$164.58	$164.60	$164.60
7 purchase totals =	$1,004.35		$1,118.3311	$1,118.33	$1,118.35	$1,118.50