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	$17.78	8.147%	$19.2285	$19.23	$19.25	$19.20
Purchase #2	$202.47	9.767%	$222.2452	$222.25	$222.25	$222.20
Purchase #3	$27.31	6.666%	$29.1305	$29.13	$29.15	$29.10
Purchase #4	$151.39	7.161%	$162.231	$162.23	$162.25	$162.20
Purchase #5	$172.52	5.156%	$181.4151	$181.42	$181.40	$181.40
Purchase #6	$59.97	9.437%	$65.6294	$65.63	$65.65	$65.60
Purchase #7	$231.35	13.348%	$262.2306	$262.23	$262.25	$262.20
7 purchase totals =	$862.79		$942.1103	$942.12	$942.20	$941.90