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	$43.28	7.593%	$46.5663	$46.57	$46.55	$46.60
Purchase #2	$68.40	6.460%	$72.8186	$72.82	$72.80	$72.80
Purchase #3	$66.41	9.233%	$72.5416	$72.54	$72.55	$72.50
Purchase #4	$197.38	12.788%	$222.621	$222.62	$222.60	$222.60
Purchase #5	$222.83	6.634%	$237.6125	$237.61	$237.60	$237.60
Purchase #6	$166.38	12.824%	$187.7166	$187.72	$187.70	$187.70
Purchase #7	$167.77	7.234%	$179.9065	$179.91	$179.90	$179.90
7 purchase totals =	$932.45		$1,019.7831	$1,019.79	$1,019.70	$1,019.70