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	$170.39	9.428%	$186.4544	$186.45	$186.45	$186.50
Purchase #2	$58.38	10.357%	$64.4264	$64.43	$64.45	$64.40
Purchase #3	$78.82	4.540%	$82.3984	$82.40	$82.40	$82.40
Purchase #4	$101.30	4.232%	$105.587	$105.59	$105.60	$105.60
Purchase #5	$76.40	13.376%	$86.6193	$86.62	$86.60	$86.60
Purchase #6	$226.96	10.332%	$250.4095	$250.41	$250.40	$250.40
Purchase #7	$50.47	9.377%	$55.2026	$55.20	$55.20	$55.20
7 purchase totals =	$762.72		$831.0976	$831.10	$831.10	$831.10