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	$94.40	6.666%	$100.6927	$100.69	$100.70	$100.70
Purchase #2	$104.28	10.684%	$115.4213	$115.42	$115.40	$115.40
Purchase #3	$212.72	4.140%	$221.5266	$221.53	$221.55	$221.50
Purchase #4	$156.46	6.303%	$166.3217	$166.32	$166.30	$166.30
Purchase #5	$205.82	11.167%	$228.8039	$228.80	$228.80	$228.80
Purchase #6	$7.81	12.401%	$8.7785	$8.78	$8.80	$8.80
Purchase #7	$122.78	3.447%	$127.0122	$127.01	$127.00	$127.00
7 purchase totals =	$904.27		$968.5569	$968.55	$968.55	$968.50