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	$190.64	10.124%	$209.9404	$209.94	$209.95	$209.90
Purchase #2	$66.27	3.465%	$68.5663	$68.57	$68.55	$68.60
Purchase #3	$169.90	8.719%	$184.7136	$184.71	$184.70	$184.70
Purchase #4	$139.64	3.445%	$144.4506	$144.45	$144.45	$144.50
Purchase #5	$59.97	9.144%	$65.4537	$65.45	$65.45	$65.50
Purchase #6	$181.64	5.164%	$191.0199	$191.02	$191.00	$191.00
Purchase #7	$110.74	3.171%	$114.2516	$114.25	$114.25	$114.30
7 purchase totals =	$918.80		$978.3961	$978.39	$978.35	$978.50