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	$56.31	5.602%	$59.4645	$59.46	$59.45	$59.50
Purchase #2	$230.60	4.293%	$240.4997	$240.50	$240.50	$240.50
Purchase #3	$98.93	4.428%	$103.3106	$103.31	$103.30	$103.30
Purchase #4	$90.40	6.566%	$96.3357	$96.34	$96.35	$96.30
Purchase #5	$173.64	7.565%	$186.7759	$186.78	$186.80	$186.80
Purchase #6	$137.89	3.736%	$143.0416	$143.04	$143.05	$143.00
Purchase #7	$155.25	12.409%	$174.515	$174.52	$174.50	$174.50
7 purchase totals =	$943.02		$1,003.9430	$1,003.95	$1,003.95	$1,003.90