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	$55.25	11.333%	$61.5115	$61.51	$61.50	$61.50
Purchase #2	$229.48	12.269%	$257.6349	$257.63	$257.65	$257.60
Purchase #3	$96.92	6.132%	$102.8631	$102.86	$102.85	$102.90
Purchase #4	$182.43	7.607%	$196.3075	$196.31	$196.30	$196.30
Purchase #5	$94.94	6.799%	$101.395	$101.40	$101.40	$101.40
Purchase #6	$108.96	13.484%	$123.6522	$123.65	$123.65	$123.70
Purchase #7	$246.33	10.348%	$271.8202	$271.82	$271.80	$271.80
7 purchase totals =	$1,014.31		$1,115.1844	$1,115.18	$1,115.15	$1,115.20