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	$85.40	7.779%	$92.0433	$92.04	$92.05	$92.00
Purchase #2	$28.32	9.687%	$31.0634	$31.06	$31.05	$31.10
Purchase #3	$236.86	5.798%	$250.5931	$250.59	$250.60	$250.60
Purchase #4	$235.59	6.213%	$250.2272	$250.23	$250.25	$250.20
Purchase #5	$144.45	11.831%	$161.5399	$161.54	$161.55	$161.50
Purchase #6	$203.26	12.464%	$228.5943	$228.59	$228.60	$228.60
Purchase #7	$137.29	13.457%	$155.7651	$155.77	$155.75	$155.80
7 purchase totals =	$1,071.17		$1,169.8263	$1,169.82	$1,169.85	$1,169.80