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	$49.25	12.341%	$55.3279	$55.33	$55.35	$55.30
Purchase #2	$136.57	7.566%	$146.9029	$146.90	$146.90	$146.90
Purchase #3	$118.80	7.639%	$127.8751	$127.88	$127.90	$127.90
Purchase #4	$62.58	11.713%	$69.91	$69.91	$69.90	$69.90
Purchase #5	$199.29	11.630%	$222.4674	$222.47	$222.45	$222.50
Purchase #6	$195.50	11.690%	$218.354	$218.35	$218.35	$218.40
Purchase #7	$201.87	10.297%	$222.6566	$222.66	$222.65	$222.70
7 purchase totals =	$963.86		$1,063.4939	$1,063.50	$1,063.50	$1,063.60