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	$52.98	5.276%	$55.7752	$55.78	$55.80	$55.80
Purchase #2	$155.46	13.591%	$176.5886	$176.59	$176.60	$176.60
Purchase #3	$108.44	3.521%	$112.2582	$112.26	$112.25	$112.30
Purchase #4	$197.45	5.773%	$208.8488	$208.85	$208.85	$208.80
Purchase #5	$57.95	11.132%	$64.401	$64.40	$64.40	$64.40
Purchase #6	$56.33	4.795%	$59.031	$59.03	$59.05	$59.00
Purchase #7	$224.31	13.838%	$255.35	$255.35	$255.35	$255.40
7 purchase totals =	$852.92		$932.2528	$932.26	$932.30	$932.30