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	$166.40	4.606%	$174.0644	$174.06	$174.05	$174.10
Purchase #2	$182.38	12.659%	$205.4675	$205.47	$205.45	$205.50
Purchase #3	$62.71	7.781%	$67.5895	$67.59	$67.60	$67.60
Purchase #4	$188.58	7.667%	$203.0384	$203.04	$203.05	$203.00
Purchase #5	$199.31	3.263%	$205.8135	$205.81	$205.80	$205.80
Purchase #6	$29.33	13.609%	$33.3215	$33.32	$33.30	$33.30
Purchase #7	$103.71	9.677%	$113.746	$113.75	$113.75	$113.70
7 purchase totals =	$932.42		$1,003.0408	$1,003.04	$1,003.00	$1,003.00