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	$91.69	9.530%	$100.4281	$100.43	$100.45	$100.40
Purchase #2	$82.94	11.517%	$92.4922	$92.49	$92.50	$92.50
Purchase #3	$138.60	11.195%	$154.1163	$154.12	$154.10	$154.10
Purchase #4	$220.87	13.337%	$250.3274	$250.33	$250.35	$250.30
Purchase #5	$94.31	3.392%	$97.509	$97.51	$97.50	$97.50
Purchase #6	$133.87	13.774%	$152.3093	$152.31	$152.30	$152.30
Purchase #7	$235.27	4.505%	$245.8689	$245.87	$245.85	$245.90
7 purchase totals =	$997.55		$1,093.0512	$1,093.06	$1,093.05	$1,093.00