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	$109.82	8.125%	$118.7429	$118.74	$118.75	$118.70
Purchase #2	$56.77	9.283%	$62.04	$62.04	$62.05	$62.00
Purchase #3	$171.40	7.597%	$184.4213	$184.42	$184.40	$184.40
Purchase #4	$74.54	10.517%	$82.3794	$82.38	$82.40	$82.40
Purchase #5	$240.57	12.811%	$271.3894	$271.39	$271.40	$271.40
Purchase #6	$216.60	3.749%	$224.7203	$224.72	$224.70	$224.70
Purchase #7	$131.63	3.787%	$136.6148	$136.61	$136.60	$136.60
7 purchase totals =	$1,001.33		$1,080.3081	$1,080.30	$1,080.30	$1,080.20