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	$166.44	9.553%	$182.34	$182.34	$182.35	$182.30
Purchase #2	$158.87	3.725%	$164.7879	$164.79	$164.80	$164.80
Purchase #3	$124.46	9.498%	$136.2812	$136.28	$136.30	$136.30
Purchase #4	$31.86	9.469%	$34.8768	$34.88	$34.90	$34.90
Purchase #5	$172.71	10.217%	$190.3558	$190.36	$190.35	$190.40
Purchase #6	$166.39	9.570%	$182.3135	$182.31	$182.30	$182.30
Purchase #7	$103.50	8.843%	$112.6525	$112.65	$112.65	$112.70
7 purchase totals =	$924.23		$1,003.6077	$1,003.61	$1,003.65	$1,003.70