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	$123.75	3.149%	$127.6469	$127.65	$127.65	$127.60
Purchase #2	$128.86	9.300%	$140.844	$140.84	$140.85	$140.80
Purchase #3	$103.87	13.696%	$118.096	$118.10	$118.10	$118.10
Purchase #4	$210.63	7.510%	$226.4483	$226.45	$226.45	$226.40
Purchase #5	$193.65	8.825%	$210.7396	$210.74	$210.75	$210.70
Purchase #6	$83.42	13.127%	$94.3705	$94.37	$94.35	$94.40
Purchase #7	$158.55	10.289%	$174.8632	$174.86	$174.85	$174.90
7 purchase totals =	$1,002.73		$1,093.0085	$1,093.01	$1,093.00	$1,092.90