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	$116.38	9.667%	$127.6305	$127.63	$127.65	$127.60
Purchase #2	$133.97	6.102%	$142.1448	$142.14	$142.15	$142.10
Purchase #3	$127.36	6.216%	$135.2767	$135.28	$135.30	$135.30
Purchase #4	$165.51	12.577%	$186.3262	$186.33	$186.35	$186.30
Purchase #5	$137.98	5.182%	$145.1301	$145.13	$145.15	$145.10
Purchase #6	$184.97	13.184%	$209.3564	$209.36	$209.35	$209.40
Purchase #7	$82.89	3.257%	$85.5897	$85.59	$85.60	$85.60
7 purchase totals =	$949.06		$1,031.4544	$1,031.46	$1,031.55	$1,031.40