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	$145.85	4.513%	$152.4322	$152.43	$152.45	$152.40
Purchase #2	$181.86	7.863%	$196.1597	$196.16	$196.15	$196.20
Purchase #3	$95.77	3.513%	$99.1344	$99.13	$99.15	$99.10
Purchase #4	$85.76	5.215%	$90.2324	$90.23	$90.25	$90.20
Purchase #5	$191.53	7.136%	$205.1976	$205.20	$205.20	$205.20
Purchase #6	$148.83	10.317%	$164.1848	$164.18	$164.20	$164.20
Purchase #7	$216.29	6.840%	$231.0842	$231.08	$231.10	$231.10
7 purchase totals =	$1,065.89		$1,138.4253	$1,138.41	$1,138.50	$1,138.40