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	$83.46	4.749%	$87.4235	$87.42	$87.40	$87.40
Purchase #2	$177.73	5.229%	$187.0235	$187.02	$187.00	$187.00
Purchase #3	$55.65	6.814%	$59.442	$59.44	$59.45	$59.40
Purchase #4	$64.64	4.170%	$67.3355	$67.34	$67.35	$67.30
Purchase #5	$85.95	3.594%	$89.039	$89.04	$89.05	$89.00
Purchase #6	$116.84	9.398%	$127.8206	$127.82	$127.80	$127.80
Purchase #7	$125.27	10.727%	$138.7077	$138.71	$138.70	$138.70
7 purchase totals =	$709.54		$756.7918	$756.79	$756.75	$756.60