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	$167.40	10.759%	$185.4106	$185.41	$185.40	$185.40
Purchase #2	$248.69	10.209%	$274.0788	$274.08	$274.10	$274.10
Purchase #3	$89.57	8.259%	$96.9676	$96.97	$96.95	$97.00
Purchase #4	$143.79	8.172%	$155.5405	$155.54	$155.55	$155.50
Purchase #5	$205.83	7.144%	$220.5345	$220.53	$220.55	$220.50
Purchase #6	$35.26	10.632%	$39.0088	$39.01	$39.00	$39.00
Purchase #7	$120.95	8.698%	$131.4702	$131.47	$131.45	$131.50
7 purchase totals =	$1,011.49		$1,103.0110	$1,103.01	$1,103.00	$1,103.00