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	$225.53	13.451%	$255.866	$255.87	$255.85	$255.90
Purchase #2	$168.33	3.790%	$174.7097	$174.71	$174.70	$174.70
Purchase #3	$88.46	9.801%	$97.13	$97.13	$97.15	$97.10
Purchase #4	$65.97	9.507%	$72.2418	$72.24	$72.25	$72.20
Purchase #5	$180.97	3.387%	$187.0995	$187.10	$187.10	$187.10
Purchase #6	$172.67	12.389%	$194.0621	$194.06	$194.05	$194.10
Purchase #7	$139.65	4.786%	$146.3336	$146.33	$146.35	$146.30
7 purchase totals =	$1,041.58		$1,127.4427	$1,127.44	$1,127.45	$1,127.40