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	$186.94	12.568%	$210.4346	$210.43	$210.45	$210.40
Purchase #2	$87.35	6.631%	$93.1422	$93.14	$93.15	$93.10
Purchase #3	$100.83	5.354%	$106.2284	$106.23	$106.25	$106.20
Purchase #4	$197.46	9.115%	$215.4585	$215.46	$215.45	$215.50
Purchase #5	$132.39	10.702%	$146.5584	$146.56	$146.55	$146.60
Purchase #6	$131.61	8.299%	$142.5323	$142.53	$142.55	$142.50
Purchase #7	$105.35	5.224%	$110.8535	$110.85	$110.85	$110.90
7 purchase totals =	$941.93		$1,025.2079	$1,025.20	$1,025.25	$1,025.20