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	$206.86	5.752%	$218.7586	$218.76	$218.75	$218.80
Purchase #2	$28.78	13.524%	$32.6722	$32.67	$32.65	$32.70
Purchase #3	$68.97	13.554%	$78.3182	$78.32	$78.30	$78.30
Purchase #4	$105.31	9.855%	$115.6883	$115.69	$115.70	$115.70
Purchase #5	$169.43	8.795%	$184.3314	$184.33	$184.35	$184.30
Purchase #6	$212.37	13.738%	$241.5454	$241.55	$241.55	$241.50
Purchase #7	$176.28	13.369%	$199.8469	$199.85	$199.85	$199.80
7 purchase totals =	$968.00		$1,071.1610	$1,071.17	$1,071.15	$1,071.10