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	$137.69	13.199%	$155.8637	$155.86	$155.85	$155.90
Purchase #2	$81.75	13.397%	$92.702	$92.70	$92.70	$92.70
Purchase #3	$238.40	8.308%	$258.2063	$258.21	$258.20	$258.20
Purchase #4	$129.79	10.472%	$143.3816	$143.38	$143.40	$143.40
Purchase #5	$31.54	12.681%	$35.5396	$35.54	$35.55	$35.50
Purchase #6	$97.87	5.703%	$103.4515	$103.45	$103.45	$103.50
Purchase #7	$233.56	7.817%	$251.8174	$251.82	$251.80	$251.80
7 purchase totals =	$950.60		$1,040.9621	$1,040.96	$1,040.95	$1,041.00