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	$84.38	12.750%	$95.1385	$95.14	$95.15	$95.10
Purchase #2	$123.27	11.495%	$137.4399	$137.44	$137.45	$137.40
Purchase #3	$114.32	3.483%	$118.3018	$118.30	$118.30	$118.30
Purchase #4	$105.44	8.452%	$114.3518	$114.35	$114.35	$114.40
Purchase #5	$81.85	4.264%	$85.3401	$85.34	$85.35	$85.30
Purchase #6	$73.64	13.653%	$83.6941	$83.69	$83.70	$83.70
Purchase #7	$72.26	10.787%	$80.0547	$80.05	$80.05	$80.10
7 purchase totals =	$655.16		$714.3209	$714.31	$714.35	$714.30