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	$31.69	5.247%	$33.3528	$33.35	$33.35	$33.40
Purchase #2	$79.46	7.408%	$85.3464	$85.35	$85.35	$85.30
Purchase #3	$116.79	8.347%	$126.5385	$126.54	$126.55	$126.50
Purchase #4	$127.96	13.678%	$145.4624	$145.46	$145.45	$145.50
Purchase #5	$114.59	5.609%	$121.0174	$121.02	$121.00	$121.00
Purchase #6	$86.91	11.523%	$96.9246	$96.92	$96.90	$96.90
Purchase #7	$77.34	10.632%	$85.5628	$85.56	$85.55	$85.60
7 purchase totals =	$634.74		$694.2049	$694.20	$694.15	$694.20