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	$148.31	12.581%	$166.9689	$166.97	$166.95	$167.00
Purchase #2	$104.47	3.320%	$107.9384	$107.94	$107.95	$107.90
Purchase #3	$89.67	11.673%	$100.1372	$100.14	$100.15	$100.10
Purchase #4	$68.59	10.166%	$75.5629	$75.56	$75.55	$75.60
Purchase #5	$72.32	8.593%	$78.5345	$78.53	$78.55	$78.50
Purchase #6	$43.73	9.631%	$47.9416	$47.94	$47.95	$47.90
Purchase #7	$240.96	11.816%	$269.4318	$269.43	$269.45	$269.40
7 purchase totals =	$768.05		$846.5153	$846.51	$846.55	$846.40