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	$148.84	10.607%	$164.6275	$164.63	$164.65	$164.60
Purchase #2	$127.65	12.168%	$143.1825	$143.18	$143.20	$143.20
Purchase #3	$89.42	10.750%	$99.0327	$99.03	$99.05	$99.00
Purchase #4	$26.29	4.224%	$27.4005	$27.40	$27.40	$27.40
Purchase #5	$168.26	3.467%	$174.0936	$174.09	$174.10	$174.10
Purchase #6	$184.92	12.500%	$208.035	$208.04	$208.05	$208.00
Purchase #7	$227.42	9.774%	$249.648	$249.65	$249.65	$249.60
7 purchase totals =	$972.80		$1,066.0198	$1,066.02	$1,066.10	$1,065.90