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	$31.70	6.751%	$33.8401	$33.84	$33.85	$33.80
Purchase #2	$206.30	5.697%	$218.0529	$218.05	$218.05	$218.10
Purchase #3	$93.35	7.293%	$100.158	$100.16	$100.15	$100.20
Purchase #4	$57.77	8.189%	$62.5008	$62.50	$62.50	$62.50
Purchase #5	$171.78	7.654%	$184.928	$184.93	$184.95	$184.90
Purchase #6	$186.63	6.165%	$198.1357	$198.14	$198.15	$198.10
Purchase #7	$135.85	7.359%	$145.8472	$145.85	$145.85	$145.80
7 purchase totals =	$883.38		$943.4627	$943.47	$943.50	$943.40