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	$134.96	4.353%	$140.8348	$140.83	$140.85	$140.80
Purchase #2	$78.83	4.498%	$82.3758	$82.38	$82.40	$82.40
Purchase #3	$241.79	12.279%	$271.4794	$271.48	$271.50	$271.50
Purchase #4	$246.49	12.207%	$276.579	$276.58	$276.60	$276.60
Purchase #5	$97.61	6.645%	$104.0962	$104.10	$104.10	$104.10
Purchase #6	$89.58	7.466%	$96.268	$96.27	$96.25	$96.30
Purchase #7	$32.82	3.382%	$33.93	$33.93	$33.95	$33.90
7 purchase totals =	$922.08		$1,005.5632	$1,005.57	$1,005.65	$1,005.60