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	$157.88	10.495%	$174.4495	$174.45	$174.45	$174.40
Purchase #2	$241.47	8.187%	$261.2391	$261.24	$261.25	$261.20
Purchase #3	$32.43	5.254%	$34.1339	$34.13	$34.15	$34.10
Purchase #4	$124.27	10.576%	$137.4128	$137.41	$137.40	$137.40
Purchase #5	$29.35	9.655%	$32.1837	$32.18	$32.20	$32.20
Purchase #6	$166.32	5.532%	$175.5208	$175.52	$175.50	$175.50
Purchase #7	$181.39	4.809%	$190.113	$190.11	$190.10	$190.10
7 purchase totals =	$933.11		$1,005.0528	$1,005.04	$1,005.05	$1,004.90