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	$57.39	3.680%	$59.502	$59.50	$59.50	$59.50
Purchase #2	$192.53	9.434%	$210.6933	$210.69	$210.70	$210.70
Purchase #3	$161.37	5.554%	$170.3325	$170.33	$170.35	$170.30
Purchase #4	$81.28	10.491%	$89.8071	$89.81	$89.80	$89.80
Purchase #5	$108.70	3.789%	$112.8186	$112.82	$112.80	$112.80
Purchase #6	$136.73	4.331%	$142.6518	$142.65	$142.65	$142.70
Purchase #7	$206.74	4.415%	$215.8676	$215.87	$215.85	$215.90
7 purchase totals =	$944.74		$1,001.6729	$1,001.67	$1,001.65	$1,001.70